WO2022165727A1 - 电极组件、电池单体、电池及电极组件的制造设备和方法 - Google Patents

电极组件、电池单体、电池及电极组件的制造设备和方法 Download PDF

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Publication number
WO2022165727A1
WO2022165727A1 PCT/CN2021/075357 CN2021075357W WO2022165727A1 WO 2022165727 A1 WO2022165727 A1 WO 2022165727A1 CN 2021075357 W CN2021075357 W CN 2021075357W WO 2022165727 A1 WO2022165727 A1 WO 2022165727A1
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WIPO (PCT)
Prior art keywords
active material
bent portion
bending
pole piece
unit area
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PCT/CN2021/075357
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English (en)
French (fr)
Inventor
金海族
许虎
李白清
李星
梁成都
Original Assignee
宁德时代新能源科技股份有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to EP21798540.7A priority Critical patent/EP4068414A4/en
Priority to CN202180008051.7A priority patent/CN115210901A/zh
Priority to PCT/CN2021/075357 priority patent/WO2022165727A1/zh
Priority to US17/562,537 priority patent/US20220246973A1/en
Publication of WO2022165727A1 publication Critical patent/WO2022165727A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H01M10/0431—Cells with wound or folded electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/75—Wires, rods or strips
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/103—Primary casings; Jackets or wrappings characterised by their shape or physical structure prismatic or rectangular
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H01M50/207—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape
    • H01M50/209—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape adapted for prismatic or rectangular cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of battery technology, and in particular, to a manufacturing apparatus and method for an electrode assembly, a battery cell, a battery, and an electrode assembly.
  • lithium-ion batteries are generally used in vehicles.
  • As a rechargeable battery lithium-ion batteries have the advantages of small size, high energy density, high power density, many cycles of use and long storage time.
  • a rechargeable battery generally includes a casing and an electrode assembly.
  • the casing is used to accommodate the electrode assembly and electrolyte.
  • the electrode assembly generally includes a positive electrode and a negative electrode, and metal ions (such as lithium ions) are used in the positive electrode and the negative electrode. move between the sheets to generate electricity.
  • Embodiments of the present application provide an electrode assembly, a battery cell, a battery, and a manufacturing apparatus and method for the electrode assembly, so as to improve the problem of unreasonable arrangement of active materials in the electrode sheet.
  • an embodiment of the present application provides an electrode assembly, including a negative electrode piece and a positive electrode piece, the negative electrode piece and the positive electrode piece are wound along a winding direction to form a winding structure, and the winding
  • the structure includes a bending area; both the negative pole piece and the positive pole piece include a plurality of bending parts located in the bending area; wherein, at least one bending part in the negative pole piece is a first bending part A folded portion, the capacity of active material per unit area outside the first folded portion is greater than the capacity of active material per unit area on the inside of the first folded portion; and/or, at least one folded portion in the positive electrode sheet is In the second bent portion, the capacity per unit area of the active material outside the second bent portion is greater than the capacity per unit area of the active material inside the second bent portion.
  • the active material capacity per unit area on the outside of the first bent portion of the negative pole piece is greater than the active material capacity per unit area on the inside of the first bent portion.
  • the arrangement of active materials in at least part of the negative electrode sheet (the region where the first bent portion is located) is more reasonable; the unit active material outside the second bent portion of the positive electrode sheet is more reasonable.
  • the capacity is greater than the capacity of the active material per unit area inside the second bending portion, and it is not easy to appear that the outer active material of the second bending portion is insufficient, and the inner active material of the second bending portion is excessive, so that at least part of the positive electrode plate ( The arrangement of the active material in the region where the second bending part is located) is more reasonable. In the electrode assembly of this structure, the arrangement of the active material in at least part of the region of the pole piece is more reasonable, and has better economy.
  • At least one bent portion in the negative electrode sheet is the first bent portion
  • at least one bent portion in the positive electrode sheet is the second bent portion
  • the The outer side of the first bent portion is arranged with the second bent portion adjacent to the first bent portion.
  • a second bending part adjacent to the first bending part is arranged on the outside of the first bending part, and the active material capacity per unit area inside the first bending part and the activity per unit area outside the second bending part are arranged.
  • the active material capacity per unit area outside the first bending portion is greater than the active material capacity per unit area inside the first bending portion
  • the active material capacity per unit area outside the second bending portion is greater than the second bending portion.
  • the capacity of the active material per unit area inside the part can increase the CB value of the outer part of the first bending part, thereby reducing the occurrence of lithium deposition.
  • At least one bent portion of the negative electrode piece is the first bent portion; and the bent portion of the positive electrode piece adjacent to the first bent portion is a third bent portion Bending part; the active material capacity per unit area outside the third bending part is equal to the active material capacity per unit area inside the third bending part.
  • the bending part adjacent to the first bending part in the positive electrode piece is the third bending part, and the active material capacity per unit area outside the first bending part is greater than the unit area inside the first bending part.
  • the active material capacity per unit area outside the third bending portion may be equal to the active material capacity per unit area inside the third bending portion, which can simplify the manufacturing process of the positive electrode sheet.
  • At least one bent portion in the positive electrode sheet is the second bent portion; and the bent portion adjacent to the second bent portion in the negative electrode sheet is a fourth bent portion Bending part; the active material capacity per unit area outside the fourth bending part is equal to the active material capacity per unit area inside the fourth bending part.
  • the bending part adjacent to the second bending part in the negative pole piece is the fourth bending part, and the active material capacity per unit area outside the second bending part is greater than the unit area inside the second bending part.
  • the active material capacity per unit area outside the fourth bent portion can be equal to the active material capacity per unit area inside the fourth bent portion, which can simplify the manufacturing process of the negative electrode sheet.
  • the first bending part includes a first current collecting part, a first active material part and a second active material part; the first current collecting part has oppositely arranged first current collecting parts in a thickness direction thereof The inner surface and the first outer surface, the first active material portion is provided on the first outer surface, and the second active material portion is provided on the first inner surface.
  • the material of the second active material portion is the same as the material of the first active material portion; the thickness of the first active material portion is greater than the thickness of the second active material portion.
  • the thickness of the first active material part is greater than the thickness of the second active material part, so that the unit of the first active material part can be
  • the area active material capacity is greater than the unit area active material capacity of the second active material portion, so that the unit area active material capacity outside the first bending portion is greater than the unit area active material capacity inside the first bending portion.
  • the first bending portion further includes a first conductive portion, the first conductive portion is connected between the second active material portion and the first inner surface, the first active material portion The thickness of the material portion is equal to or greater than the total thickness of the second active material portion and the first conductive portion.
  • the thickness of the first active material portion is equal to or greater than the total thickness of the second active material portion and the first conductive portion, In order to realize that the thickness of the first active material portion is greater than the thickness of the second active material portion.
  • the thickness of the first active material portion is equal to the thickness of the second active material portion; the gram capacity of the active material in the first active material portion is greater than that in the second active material portion The gram capacity of the active material.
  • the active material capacity per unit area of the first active material part can be made larger than the active material capacity per unit area of the second active material part, so that the active material capacity per unit area outside the first bending part is greater than the unit area inside the first bending part. Area active material capacity.
  • the second bending part includes a second current collecting part, a third active material part and a fourth active material part; the second current collecting part has a second current collecting part oppositely arranged in its thickness direction The inner surface and the second outer surface, the third active material portion is provided on the second outer surface, and the fourth active material portion is provided on the second inner surface.
  • the material of the fourth active material portion is the same as the material of the third active material portion; the thickness of the third active material portion is greater than the thickness of the fourth active material portion.
  • the thickness of the third active material portion is greater than the thickness of the fourth active material portion, so that the third active material portion can be
  • the active material capacity per unit area is greater than that of the fourth active material portion, so that the active material capacity per unit area outside the second bending portion is greater than the active material capacity per unit area inside the second bending portion.
  • the second bending portion further includes a second conductive portion, the second conductive portion is connected between the fourth active material portion and the second inner surface, and the third active material portion The thickness of the material portion is equal to or greater than the total thickness of the fourth active material portion and the second conductive portion.
  • the thickness of the third active material portion is equal to or greater than the total thickness of the fourth active material portion and the second conductive portion, In order to realize that the thickness of the third active material portion is greater than the thickness of the fourth active material portion.
  • the thickness of the third active material portion is equal to the thickness of the fourth active material portion; the gram capacity of the active material in the third active material portion is greater than that in the fourth active material portion The gram capacity of the active material.
  • the active material capacity per unit area of the third active material part can be made larger than the active material capacity per unit area of the fourth active material part, so that the active material capacity per unit area outside the second bending part is greater than the unit area inside the second bending part. Area active material capacity.
  • the negative electrode sheet includes a negative electrode current collector and negative electrode active material layers disposed on both sides of the negative electrode current collector in the thickness direction; each negative electrode active material layer is equally thickly distributed along the winding direction on all the negative electrode active material layers. the negative current collector.
  • each negative electrode active material layer is distributed on the positive electrode current collector with equal thickness along the winding direction, which simplifies the manufacturing process of the negative electrode pole piece and helps to reduce the production cost.
  • the positive electrode sheet includes a positive electrode current collector and positive electrode active material layers disposed on both sides in the thickness direction of the positive electrode current collector; each positive electrode active material layer is equally thickly distributed along the winding direction on all the positive electrode active material layers. the positive current collector.
  • each positive electrode active material layer is distributed on the positive electrode current collector with equal thickness along the winding direction, which simplifies the manufacturing process of the positive electrode sheet and helps to reduce the production cost.
  • all the bent portions in the negative pole piece are the first bent portions.
  • all the bent parts in the negative pole piece are the first bent parts, that is, all the bent parts in the negative pole piece are the outer unit active material capacity greater than the inner unit active material capacity, so that the negative pole piece is
  • the arrangement of the active material in the part located in the bending area is more reasonable.
  • the capacity of the active material per unit area inside the first bending part meets the design requirements, since the capacity per unit area of the active material outside the first bending part is larger than that inside the first bending part, it is equivalent to increasing the capacity of the active material per unit area inside the first bending part.
  • the capacity of active material per unit area outside a bent portion increases the CB value of the outer portion of all bent portions in the negative electrode sheet, and the portion of the negative electrode sheet located in the bent region is less prone to lithium precipitation.
  • all the bent portions in the positive pole piece are the second bent portions.
  • all the bent parts in the positive electrode piece are the second bent parts, that is, all the bent parts in the positive electrode piece are the outer unit active material capacity greater than the inner unit active material capacity, so that the positive electrode electrode piece is
  • the arrangement of the active material in the part located in the bending area is more reasonable.
  • the capacity of the active material per unit area outside the second bending part meets the design requirements, since the capacity per unit area of the active material outside the second bending part is greater than the capacity per unit area of the active material inside the second bending part, it is equivalent to reducing the amount of active material per unit area.
  • the capacity per unit area of the active material inside the two bending parts increases the CB value of the outer parts of the multiple bending parts in the negative pole piece, and the part of the negative pole piece located in the bending area is not prone to lithium precipitation.
  • an embodiment of the present application provides a battery cell, including a casing and the electrode assembly provided by any embodiment of the first aspect; the electrode assembly is accommodated in the casing.
  • an embodiment of the present application provides a battery, including a box body and the battery cell provided by any one of the embodiments of the second aspect; the battery cell is accommodated in the box body.
  • an embodiment of the present application provides an electrical device, including the battery provided by any one of the embodiments of the second aspect.
  • an embodiment of the present application provides a method for manufacturing an electrode assembly, including:
  • a positive pole piece and a negative pole piece are provided; the negative pole piece and the positive pole piece are wound along the winding direction to form a winding structure; wherein, the winding structure includes a bending area, and the negative pole piece and the positive pole piece include a plurality of bending parts located in the bending area; at least one bending part in the negative pole piece is a first bending part, and the unit outside the first bending part is The area active material capacity is greater than the unit area active material capacity inside the first bent portion; and/or, at least one bent portion in the positive electrode sheet is a second bent portion, and the second bent portion The active material capacity per unit area on the outside is larger than the active material capacity per unit area on the inside of the second bent portion.
  • an embodiment of the present application further provides a device for manufacturing an electrode assembly, including: a device for providing a positive electrode and a negative electrode; an assembling device for assembling the negative electrode and the positive electrode
  • the sheet is wound along the winding direction to form a winding structure; wherein, the winding structure includes a bending area, and both the negative pole piece and the positive pole piece include a plurality of bending parts located in the bending area ; At least one bent portion in the negative pole piece is a first bent portion, and the active material capacity per unit area on the outside of the first bent portion is greater than the active material capacity per unit area on the inside of the first bent portion; And/or, at least one bent portion in the positive electrode sheet is a second bent portion, and the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area inside the second bent portion. material capacity.
  • FIG. 1 is a schematic structural diagram of a vehicle provided by some embodiments of the present application.
  • FIG. 2 is an exploded view of a battery provided by some embodiments of the present application.
  • FIG. 3 is a schematic structural diagram of the battery module shown in FIG. 2;
  • FIG. 4 is an exploded view of the battery cell shown in FIG. 3;
  • FIG. 5 is a schematic structural diagram of an electrode assembly provided by some embodiments of the present application.
  • FIG. 6 is a schematic structural diagram of electrode assemblies provided by further embodiments of the present application.
  • Fig. 7 is a partial enlarged view of the electrode assembly shown in Fig. 5;
  • FIG. 8 is a partial enlarged view of a portion of an electrode assembly located in a bending region provided by some embodiments of the present application;
  • FIG. 9 is a partial enlarged view of a portion of an electrode assembly located in a bending region according to further embodiments of the present application.
  • Fig. 10 is a partial enlarged view of the portion of the electrode assembly located in the bending region provided by further embodiments of the present application;
  • FIG. 11 is a partial enlarged view of a portion of the electrode assembly located in the bending region provided by other embodiments of the present application;
  • FIG. 12 is a partial enlarged view of the portion of the electrode assembly located in the bending region according to further embodiments of the present application.
  • FIG. 13 is a flowchart of a method for manufacturing an electrode assembly provided by some embodiments of the present application.
  • FIG. 14 is a schematic block diagram of a manufacturing apparatus of an electrode assembly provided by some embodiments of the present application.
  • the terms “installed”, “connected”, “connected” and “attached” should be understood in a broad sense, for example, it may be a fixed connection, It can also be a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be internal communication between two components.
  • installed should be understood in a broad sense, for example, it may be a fixed connection, It can also be a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be internal communication between two components.
  • plural refers to two or more (including two).
  • the battery cells may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, etc., which are not limited in the embodiments of the present application.
  • the battery cell may be in the form of a cylinder, a flat body, a rectangular parallelepiped, or other shapes, which are not limited in the embodiments of the present application.
  • the battery cells are generally divided into three types according to the packaging method: cylindrical battery cells, square battery cells, and soft-pack battery cells, which are not limited in the embodiments of the present application.
  • the battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.
  • the batteries mentioned in this application may include battery modules or battery packs, and the like.
  • Batteries typically include a case for enclosing one or more battery cells. The box can prevent liquids or other foreign objects from affecting the charging or discharging of the battery cells.
  • the battery cell includes an electrode assembly and an electrolyte, and the electrode assembly is composed of a positive electrode sheet, a negative electrode sheet and a separator.
  • the battery cell mainly relies on the movement of metal ions between the positive and negative plates to work.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is coated on the surface of the positive electrode current collector, and the positive electrode current collector without the positive electrode active material layer protrudes from the positive electrode current collector that has been coated with the positive electrode active material layer. , the positive electrode current collector without the positive electrode active material layer is used as the positive electrode tab.
  • the material of the positive electrode current collector can be aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganate.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer is coated on the surface of the negative electrode current collector, and the negative electrode current collector without the negative electrode active material layer protrudes from the negative electrode current collector that has been coated with the negative electrode active material layer. , the negative electrode current collector without the negative electrode active material layer is used as the negative electrode tab.
  • the material of the negative electrode current collector can be copper, and the negative electrode active material can be carbon or silicon.
  • the number of positive tabs is multiple and stacked together, and the number of negative tabs is multiple and stacked together.
  • the material of the isolation film may be PP (polypropylene, polypropylene) or PE (polyethylene, polyethylene) or the like.
  • the electrode assembly may be a wound structure or a laminated structure, and the embodiment of the present application is not limited thereto.
  • the thickness of the inner active material layer of the negative pole piece in the electrode assembly is equal to the thickness of the outer active material layer of the negative pole piece, and the material of the inner active material layer of the negative pole piece is the same as the material of the outer active material layer;
  • the thickness of the inner active material layer of the pole piece is equal to that of the outer active material layer of the positive pole piece, and the material of the inner active material layer of the positive pole piece is the same as the active material of the outer active material layer; in the bending area of the electrode assembly, the negative electrode
  • the radius of the inner active material layer of the pole piece is larger than the radius of the outer active material layer of the positive pole piece located inside the negative pole piece, and the radius of the outer active material layer of the negative pole piece will be smaller than the radius of the positive pole piece outside the negative pole piece.
  • the radius of the inner active material layer so that the inner active material of the bending part of the negative pole piece in the bending area is excessive, and the outer active material is insufficient. Similarly, it may also occur that the positive pole piece is in the bending area. The outer active material of the bent part is insufficient and the inner active material is excessive.
  • the electrode assembly of this structure has unreasonable arrangement of the active material in the pole piece, and is less economical.
  • the negative electrode piece includes a first bending portion located in the bending region, and the active material capacity per unit area outside the first bending portion is greater than the unit area inside the first bending portion.
  • Area active material capacity, and/or, the positive pole piece includes a second bending portion located in the bending region, and the active material capacity per unit area outside the second bending portion is greater than the active material capacity per unit area inside the second bending portion .
  • Electrical equipment can be vehicles, mobile phones, portable devices, notebook computers, ships, spacecraft, electric toys and power tools, and so on.
  • Vehicles can be fuel vehicles, gas vehicles or new energy vehicles, and new energy vehicles can be pure electric vehicles, hybrid vehicles or extended-range vehicles, etc.
  • spacecraft include airplanes, rockets, space shuttles, spacecraft, etc.
  • electric toys include fixed Electric toys that are portable or mobile, such as game consoles, electric car toys, electric ship toys and electric airplane toys, etc.
  • electric tools include metal cutting power tools, grinding power tools, assembling power tools and railway power tools, such as, Electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, electric impact drills, concrete vibrators and electric planers, etc.
  • the embodiments of the present application do not impose special restrictions on the above-mentioned electrical equipment.
  • the electric device is a vehicle as an example for description.
  • FIG. 1 is a schematic structural diagram of a vehicle 1000 according to some embodiments of the present application.
  • a battery 100 is disposed inside the vehicle 1000 , and the battery 100 may be disposed at the bottom, head or tail of the vehicle 1000 .
  • the battery 100 may be used for power supply of the vehicle 1000 , for example, the battery 100 may be used as an operating power source of the vehicle 1000 .
  • the vehicle 1000 may also include a controller 200 and a motor 300 for controlling the battery 100 to supply power to the motor 300 , eg, for starting, navigating, and running the vehicle 1000 for work power requirements.
  • the battery 100 can not only be used as the operating power source of the vehicle 1000, but also can be used as the driving power source of the vehicle 1000 to provide driving power for the vehicle 1000 instead of or partially instead of fuel or natural gas.
  • FIG. 2 is an exploded view of a battery 100 provided by some embodiments of the application.
  • the battery 100 includes a case 10 and a battery cell 20 (not shown in FIG. 2 ), and the battery cell 20 is accommodated in the case 10 .
  • the case 10 is used for accommodating the battery cells 20 , and the case 10 may have various structures.
  • the case 10 may include a first part 11 and a second part 12 , the first part 11 and the second part 12 are mutually covered, and the first part 11 and the second part 12 together define a space for accommodating the battery cells 20 accommodating space 13.
  • the second part 12 can be a hollow structure with one end open, the first part 11 is a plate-like structure, and the first part 11 is covered with the opening side of the second part 12 to form a box 10 with an accommodating space 13; the first part 11 and The second part 12 can also be a hollow structure with one side open, and the opening side of the first part 11 is covered with the opening side of the second part 12 to form the box 10 with the accommodating space 13 .
  • the first part 11 and the second part 12 may have various shapes, such as a cylinder, a rectangular parallelepiped, and the like.
  • a sealing member such as a sealant, a sealing ring, etc., may also be arranged between the first part 11 and the second part 12 .
  • the first part 11 can also be called an upper cover, and the second part 12 can also be called a lower case.
  • the battery 100 there may be one battery cell 20 or a plurality of battery cells 20 . If there are a plurality of battery cells 20, the plurality of battery cells 20 may be connected in series or in parallel or in a mixed connection.
  • a mixed connection means that the plurality of battery cells 20 are both connected in series and in parallel.
  • the plurality of battery cells 20 can be directly connected in series or in parallel or mixed together, and then the whole formed by the plurality of battery cells 20 is accommodated in the box 10; of course, the plurality of battery cells 20 can also be connected in series first.
  • the battery modules 30 are formed in parallel or in a mixed connection, and a plurality of battery modules 30 are connected in series or in parallel or in a mixed connection to form a whole, and are accommodated in the box body 10 .
  • FIG. 3 is a schematic structural diagram of the battery module 30 shown in FIG. 2 .
  • There are a plurality of battery cells 20 and the plurality of battery cells 20 are first connected in series or in parallel or mixed to form a battery module 30 .
  • a plurality of battery modules 30 are connected in series or in parallel or mixed to form a whole, and are accommodated in the box 10 .
  • the plurality of battery cells 20 in the battery module 30 can be electrically connected through the bus component 31 to realize parallel connection, series connection or mixed connection of the plurality of battery cells 20 in the battery module 30 .
  • FIG. 4 is an exploded view of the battery cell 20 shown in FIG. 3 .
  • the battery cell 20 provided in the embodiment of the present application includes a casing 21 and an electrode assembly 22 , and the electrode assembly 22 is accommodated in the casing 21 .
  • the housing 21 may also be used to contain an electrolyte, such as an electrolyte.
  • the housing 21 may have various structural forms.
  • the housing 21 may include a housing 211 and a cover 212, the housing 211 is a hollow structure with an opening on one side, and the cover 212 covers the opening of the housing 211 and forms a sealing connection to form a A sealed space 213 that accommodates the electrode assembly 22 and the electrolyte.
  • the electrode assembly 22 can be put into the casing 211 first, and the electrolyte is filled into the casing 211, and then the cover body 212 is closed on the opening of the casing 211.
  • the housing 211 may be in various shapes, such as a cylinder, a rectangular parallelepiped, and the like.
  • the shape of the case 211 may be determined according to the specific shape of the electrode assembly 22 .
  • the cover body 212 may also have various structures, for example, the cover body 212 is a plate-like structure, a hollow structure with one end open, and the like.
  • the casing 211 is a rectangular parallelepiped structure
  • the cover body 212 is a plate-like structure
  • the cover body 212 covers the opening at the top of the casing 211 .
  • the battery cell 20 may further include a positive electrode terminal 214 , a negative electrode terminal 215 and a pressure relief mechanism 216 , and the positive electrode terminal 214 , the negative electrode terminal 215 and the pressure relief mechanism 216 are all mounted on the cover body 212 . Both the positive electrode terminal 214 and the negative electrode terminal 215 are used for electrical connection with the electrode assembly 22 to output electric energy generated by the electrode assembly 22 .
  • the pressure relief mechanism 216 is used to release the pressure inside the battery cell 20 when the internal pressure or temperature of the battery cell 20 reaches a predetermined value.
  • the pressure relief mechanism 216 is located between the positive electrode terminal 214 and the negative electrode terminal 215, and the pressure relief mechanism 216 may be a component such as an explosion-proof valve, a rupture disk, a gas valve, a pressure relief valve or a safety valve.
  • the housing 21 may also have other structures.
  • the housing 21 includes a housing 211 and two covers 212 , the housing 211 is a hollow structure with openings on opposite sides, and one cover 212 corresponds to the cover It is closed at one opening of the casing 211 and forms a sealed connection to form a sealed space 213 for accommodating the electrode assembly 22 and the electrolyte.
  • the positive electrode terminal 214 and the negative electrode terminal 215 can be installed on the same cover 212, or can be installed on different covers 212; a pressure relief mechanism 216 can be installed on one cover 212, The pressure relief mechanism 216 may also be installed on the two cover bodies 212 .
  • the number of electrode assemblies 22 accommodated in the casing 21 may be one or a plurality of them. Illustratively, in FIG. 4 , there are two electrode assemblies 22 .
  • FIG. 5 is a schematic structural diagram of an electrode assembly 22 provided by some embodiments of the present application.
  • the electrode assembly 22 includes a negative pole piece 220 and a positive pole piece 221 , and the negative pole piece 220 and the positive pole piece 221 are along the winding direction A
  • the winding structure includes a bending area B, and the negative pole piece 220 and the positive pole piece 221 each include a plurality of bending parts 223 located in the bending area B.
  • At least one bent portion 223 in the negative pole piece 220 is a first bent portion 224 (not shown in FIG. 5 ), and the active material capacity per unit area outside the first bent portion 224 is greater than that inside the first bent portion 224 and/or, at least one bent portion 223 in the positive electrode sheet 221 is a second bent portion 225 (not shown in FIG. 5 ), and the active material per unit area outside the second bent portion 225 The capacity is larger than the capacity per unit area of the active material inside the second bent portion 225 .
  • the capacity of active material per unit area outside the first bent portion 224 of the negative pole piece 220 is greater than the capacity of active material per unit area inside the first bent portion 224, the active material inside the first bent portion 224 is less likely to be excessive, and the second In the case where the outer active material of a bent portion 224 is insufficient, the arrangement of the active material in at least a part of the negative pole piece 220 (the region where the first bent portion 224 is located) is more reasonable.
  • the capacity of active material per unit area outside the second bent portion 225 of the positive electrode piece 221 is greater than the capacity of active material per unit area inside the second bent portion 225, it is unlikely that the active material on the outside of the second bent portion 225 is insufficient, and the second The excess of active material inside the bent portion 225 makes the arrangement of the active material in at least a part of the positive electrode sheet 221 (the region where the second bent portion 225 is located) more reasonable. In the electrode assembly 22 with this structure, the arrangement of the active material in at least a part of the pole piece is more reasonable and has better economy.
  • the capacity of the active material per unit area inside the first bending portion 224 meets the design requirements, that is, the capacity of the active material per unit area inside the first bending portion 224 reaches the first preset value, so that the inner portion of the first bending portion 224 Lithium precipitation is not easy to occur, because the capacity of active material per unit area outside the first bending portion 224 is greater than the capacity of active material per unit area inside the first bending portion 224, which is equivalent to increasing the first bending portion relative to the first preset value.
  • the capacity of the active material per unit area outside the folded portion 224 can increase the CB value of the outer portion of the first folded portion 224 , thereby making the outer portion of the first folded portion 224 less prone to lithium precipitation.
  • the capacity of the active material per unit area outside the second bending portion 225 meets the design requirements, that is, the capacity of the active material per unit area outside the second bending portion 225 reaches the second preset value, so that the negative electrode pole piece 220 is located at the second bending portion.
  • the inner portion of the bent portion 223 on the outer side of the portion 225 is not prone to lithium precipitation.
  • the capacity of the active material per unit area outside the second bent portion 225 is larger than the capacity of the active material per unit area inside the second bent portion 225, the capacity of the active material per unit area is higher than that of the second pre-
  • the setting value is equivalent to reducing the active material capacity per unit area on the inside of the second bending portion 225, so that the outer portion of the bending portion 223 where the negative electrode pole piece 220 is located on the inner side of the second bending portion 225 is also less prone to lithium precipitation. .
  • the CB (Cell Balance) value is the ratio of the capacity of the negative electrode active material per unit area to the capacity of the positive electrode active material per unit area.
  • the CB (Cell Balance) value of the outer portion of the bent portion 223 of the negative electrode pole piece 220 Q1/Q2, wherein the active material capacity per unit area of the active material on the outer side of one bent portion 223 in the negative electrode pole piece 220 is Q1 , the active material capacity per unit area of the active material inside the bent portion 223 adjacent to the one bent portion 223 in the positive electrode piece 221 is Q2.
  • the winding direction A is the direction in which the positive pole piece 221 and the negative pole piece 220 are wound circumferentially from the inside to the outside.
  • the winding direction A is the clockwise direction.
  • the electrode assembly 22 may further include a separator 222 for separating the positive electrode 221 and the negative electrode 220 to reduce the risk of short circuit between the positive electrode 221 and the negative electrode 220 .
  • the material of the isolation film 222 may be PP (polypropylene, polypropylene) or PE (polyethylene, polyethylene).
  • the winding structure further includes a straight area C, the straight area C is connected with the bending area B, and the opposite ends of the straight area C may be provided with the bending area B.
  • the flat region C is the region where the winding structure has a flat structure, and the portion of the positive pole piece 221 in the flat region C and the portion of the negative pole piece 220 in the flat region C are arranged substantially flat.
  • the bending area B is the area where the winding structure has a bending structure, the part of the positive pole piece 221 located in the bending area B (the bending part 223 ) and the part of the negative pole piece 220 located in the bending area B (the bending part 223 ) ) are flexurally distributed.
  • both the bent portion 223 of the positive pole piece 221 and the bent portion 223 of the negative pole piece 220 are at least partially arc-shaped.
  • the winding structure includes a straight area C and a bending area B, and the electrode assembly is a flat body as a whole.
  • first bending portion 224 is arranged in the bending area B
  • the second bending portion 225 may be arranged in only one bending area B, or it may be Second bending portions 225 are arranged in both bending regions B. As shown in FIG.
  • the plurality of bending parts 223 in the positive electrode pole piece 221 and the plurality of bending parts 223 in the negative electrode pole piece 220 are alternately arranged, that is, when bending In area B, one bent portion 223 of the negative pole piece 220 , one bent portion 223 of the positive pole piece 221 , one bent portion 223 of the negative pole piece 220 . . . are arranged in order.
  • FIG. 6 is a schematic structural diagram of the electrode assembly 22 provided by further embodiments of the present application.
  • the electrode assembly 22 can be a cylinder as a whole.
  • a circle of the positive pole piece 221 is a bending portion 223 ;
  • a circle of the negative pole piece 220 is a bending portion 223 .
  • FIG. 7 is a partial enlarged view of the electrode assembly 22 shown in FIG. 5 .
  • the negative electrode sheet 220 includes a negative electrode current collector 2201 and a negative electrode current collector 2201 disposed on both sides in the thickness direction of the negative electrode current collector 2201 .
  • the negative electrode active material layer, the negative electrode active material layers on both sides of the negative electrode current collector 2201 in the thickness direction are the first negative electrode active material layer 2202 and the second negative electrode active material layer 2203 respectively, and the first negative electrode active material layer 2202 is provided in the negative electrode current collector.
  • the second negative electrode active material layer 2203 is provided on the inner surface of the negative electrode current collector 2201.
  • the positive electrode sheet 221 includes a positive electrode current collector 2211 and a positive electrode active material layer disposed on both sides of the positive electrode current collector 2211 in the thickness direction, and the positive electrode active material layers on both sides of the positive electrode current collector 2211 in the thickness direction are respectively the first positive electrode active material.
  • Layer 2212 and second positive active material layer 2213, the first positive active material layer 2212 is provided on the outer surface of the positive current collector 2211, and the second positive active material layer 2213 is provided on the inner surface of the positive current collector 2211.
  • the negative electrode current collector 2201 may have a portion that is not coated with the negative electrode active material layer, which is the negative electrode tab (not shown in the figure); the positive electrode current collector 2211 may have a portion that is not coated with the negative electrode active material layer, and this portion is Positive tab (not shown).
  • the positive tab is used for electrical connection with the positive electrode terminal 214 (see FIG. 4 ), and the negative tab is used for electrical connection with the negative electrode terminal 215 (see FIG. 4 ).
  • each negative electrode active material layer is equally thickly distributed along the winding direction A on the negative electrode current collector 2201, that is, the first negative electrode active material layer 2202 is equally thickly distributed along the winding direction A on the negative electrode current collector 2201.
  • the negative electrode current collector 2201 and the second negative electrode active material layer 2203 are distributed in the negative electrode current collector 2201 in the same thickness along the winding direction A. This structure can simplify the manufacturing process of the negative pole piece 220, which is beneficial to reduce the production cost.
  • each layer of the first negative electrode active material layer 2202 located in the bending region B is equal to the thickness of each layer of the first negative electrode active material layer 2202 located in the flat region C; the second negative electrode active material layer 2203 is located in the curved region.
  • the thickness of each layer of the folded region B is equal to the thickness of each layer of the second negative electrode active material layer 2203 located in the flat region C.
  • each positive electrode active material layer is distributed on the positive electrode current collector 2211 with the same thickness along the winding direction A, that is, the first positive electrode active material layer 2212 is equally distributed along the winding direction A on the positive electrode current collector 2211 .
  • the positive electrode current collector 2211 and the second positive electrode active material layer 2213 are distributed in the positive electrode current collector 2211 with the same thickness along the winding direction A. This structure can simplify the manufacturing process of the positive pole piece 221, which is beneficial to reduce the production cost.
  • each layer of the first positive electrode active material layer 2212 located in the bending region B is equal to the thickness of each layer of the first positive electrode active material layer 2212 located in the flat region C; the second positive electrode active material layer 2213 is located in the curved region.
  • the thickness of each layer of the folded region B is equal to the thickness of each layer of the second positive electrode active material layer 2213 located in the flat region C.
  • FIG. 8 is a partial enlarged view of a portion of the electrode assembly 22 located in the bending region B according to some embodiments of the present application, and at least one bending portion 223 in the negative pole piece 220 is the first In a bent portion 224 , the active material capacity per unit area outside the first bent portion 224 of the negative pole piece 220 is greater than the active material capacity per unit area inside the first bent portion 224 .
  • the bent portion 223 adjacent to the first bent portion 224 in the positive electrode piece 221 is the third bent portion 226 , and the active material capacity per unit area outside the third bent portion 226 is equal to the unit of the inside of the third bent portion 226 .
  • Area active material capacity is a partial enlarged view of a portion of the electrode assembly 22 located in the bending region B according to some embodiments of the present application, and at least one bending portion 223 in the negative pole piece 220 is the first In a bent portion 224 , the active material capacity per unit area outside the first bent portion 224 of the negative pole piece 2
  • the active material capacity per unit area outside the first bending portion 224 is greater than the active material capacity per unit area inside the first bending portion 224
  • the active material capacity per unit area outside the third bending portion 226 may be equal to the third bending portion 226.
  • the capacity of the active material per unit area inside the folded portion 226 is to simplify the manufacturing process of the positive electrode sheet 221 .
  • the first bending portion 224 includes a first current collecting portion 2241 , a first active material portion 2242 and a second active material portion 2243 .
  • the first current collecting portion 2241 has a first inner surface 2241a and a first outer surface 2241b arranged opposite to each other in the thickness direction, the first active material portion 2242 is provided on the first outer surface 2241b, and the second active material portion 2243 is provided on the first outer surface 2241b.
  • the third bent portion 226 includes a third current collecting portion 2261 , a fifth active material portion 2262 and a sixth active material portion 2263 .
  • the third current collecting portion 2261 has a third inner surface 2261a and a third outer surface 2261b arranged opposite to each other in the thickness direction, the fifth active material portion 2262 is provided on the third outer surface 2261b, and the sixth active material portion 2263 is provided on the third outer surface 2261b. Three inner surfaces 2261a.
  • the first current collecting portion 2241 is a layer of the negative electrode current collector 2201 (see FIG. 7 ) in the bending region B
  • the first active material portion 2242 is the first negative electrode active material layer 2202 (see FIG. 7 ) in the bending region.
  • One layer of the bending region B, the second active material portion 2243 is a layer of the second negative electrode active material layer 2203 (see FIG. 7 ) in the bending region B.
  • the third current collector portion 2261 is a layer of the positive electrode current collector 2211 (see FIG. 7 ) in the bending region B
  • the fifth active material portion 2262 is the first positive electrode active material layer 2212 (see FIG. 7 ) in the bending region B.
  • the sixth active material part 2263 is a layer of the second positive electrode active material layer 2213 (see FIG. 7 ) in the bending region B.
  • the active material capacity per unit area outside the first bent portion 224 is larger than the active material capacity per unit area inside the first bent portion 224 , that is, the activity per unit area of the first active material portion 2242 (outer portion of the first bent portion 224 ).
  • the material capacity is larger than the active material capacity per unit area of the second active material portion 2243 (the inner portion of the first bent portion 224 ).
  • the active material capacity per unit area outside the first bent portion 224 may be the ratio of the active material capacity of the first active material portion 2242 to the area of the first outer surface 2241b, and the active material capacity per unit area inside the first bent portion 224 may be is the ratio of the active material capacity of the second active material portion 2243 to the area of the first inner surface 2241a.
  • the active material capacity per unit area outside the third bent portion 226 is equal to the active material capacity per unit area inside the third bent portion 226 , that is, the activity per unit area of the fifth active material portion 2262 (outer portion of the third bent portion 226 ).
  • the material capacity is equal to the active material capacity per unit area of the sixth active material portion 2263 (the inner portion of the third bent portion 226 ).
  • the active material capacity per unit area outside the third bending portion 226 may be the ratio of the active material capacity of the fifth active material portion 2262 to the area of the third outer surface 2261b, and the active material capacity per unit area inside the third bending portion 226 may be is the ratio of the active material capacity of the sixth active material portion 2263 to the third inner surface 2261a.
  • all the bent portions 223 may be the first bent portions 224 , or some of the bent portions 223 may be the first bent portions 224 . If all the bent portions 223 in the negative electrode sheet 220 are the first bent portions 224 , the active material capacity per unit area outside all the bent portions 223 in the negative electrode sheet 220 is larger than the active material capacity per unit area inside. If only part of the bent portion 223 of the negative electrode piece 220 is the first bent portion 224, all the bent portions 223 of the negative electrode piece 220 except the first bent portion 224 can be made of an outer active material whose capacity per unit area is equal to the inner one. The structure of the active material capacity per unit area. In the positive pole piece 221 , all the bent portions 223 may be the third bent portions 226 , or only part of the bent portions 223 may be the third bent portions 226 .
  • some of the bent portions 223 in the negative pole piece 220 are the first bent portions 224 , and all the bent portions 223 in the positive pole piece 221 are the third bent portions 226 .
  • one or more bending portions 223 that may be at the innermost side of the bending region B are the first bending portions 224 .
  • the two innermost bending parts 223 in the negative pole piece 220 are the first bending parts 224 .
  • all the bent portions 223 in the negative pole piece 220 are the first bent portions 224
  • all the bent portions 223 in the positive pole piece 221 are the third bent portions 226 .
  • each negative active material layer may be distributed on the negative current collector 2201 with equal thickness along the winding direction A; in the positive pole piece 221, each positive active material layer may be distributed along the winding direction A along The winding direction A is distributed in the positive electrode current collector 2211 with the same thickness.
  • the active material capacity per unit area outside the first bending portion 224 may be greater than the active material capacity per unit area inside the first bending portion 224 in various ways.
  • the material of the first active material portion 2242 in the first bending portion 224 is the same as the material of the second active material portion 2243 , and the thickness of the first active material portion 2242 is greater than that of the second active material portion 2242 .
  • the thickness of the active material portion 2243 is the same as the material of the second active material portion 2243 .
  • the thickness of the first active material portion 2242 is greater than the thickness of the second active material portion 2243, so that the thickness of the first active material portion 2242 can be reduced.
  • the active material capacity per unit area is greater than that of the second active material portion 2243 , so that the active material capacity per unit area outside the first bending portion 224 is greater than the active material capacity per unit area inside the first bending portion 224 .
  • the material of the first active material part 2242 is the same as the material of the second active material part 2243 , that is, the first inner surface 2241a and the first outer surface 2241b of the first current collecting part 2241 are coated with the same active material Department of Matter. It can be understood that the components of the first active material part 2242 are the same as the components of the second active material part 2243 , and the proportion of each component of the first active material part 2242 is the same as that of the second active material part 2243 .
  • the first active material part 2242 and the second active material part 2243 both include active materials, conductive agents and adhesives, and the proportion of the active material in the first active material part 2242 is the same as the active material in the second active material part 2243.
  • the proportion of the material is the same, the proportion of the conductive agent in the first active material part 2242 is the same as the proportion of the conductive agent in the second active material part 2243, and the proportion of the adhesive in the first active material part 2242 is the same as the proportion of the conductive agent in the first active material part 2242.
  • the proportion of the adhesive in the second active material portion 2243 is the same.
  • the thickness of the first active material portion 2242 is greater than that of the second active material portion 2243 by 0.5%-20%.
  • the thickness of the first active material portion 2242 is greater than that of the second active material portion 2243 by 1.5%-12%.
  • one or more bending portions 223 of the negative electrode pole piece 220 at the innermost part of the bending area B are the first bending parts 224 , they may be the first negative electrode active material in one or more turns of the innermost circle of the negative electrode pole piece 220 .
  • the thickness of the layer 2202 is greater than the thickness of the second negative electrode active material layer 2203 . Taking the two innermost bending parts 223 of the negative electrode pole piece 220 in the bending area B as the first bending parts 224 as an example, they can be the two innermost circles of the first negative electrode active material layer 2202 of the negative electrode pole piece 220 .
  • the thickness is greater than the thickness of the second negative electrode active material layer 2203, so that the thickness of the first active material portion 2242 of the first bending portion 224 is greater than the thickness of the second active material portion 2243, so that the two innermost circles of the negative electrode pole piece 220 A bent portion 224 is not prone to the phenomenon of lithium deposition, which can not only improve the safety of the battery cell 20 but also reduce the production cost.
  • FIG. 9 is a partial enlarged view of a portion of the electrode assembly 22 located in the bending region B according to further embodiments of the present application.
  • the first bending portion 224 further includes a first conductive portion 228 , the first conductive portion 228 is connected between the second active material portion 2243 and the first inner surface 2241a of the first current collecting portion 2241, and the thickness of the first active material portion 2242 is equal to or greater than that of the second active material portion 2243 and the first The total thickness of the conductive portion 228 .
  • the thickness of the first active material portion 2242 is equal to or greater than that of the second active material portion 2243 and the first conductive portion 2242.
  • the total thickness of the portion 228 is adjusted so that the thickness of the first active material portion 2242 is greater than the thickness of the second active material portion 2243 .
  • the thickness of the first active material portion 2242 can be realized as follows: larger than the thickness of the second active material portion 2243 .
  • the first conductive part 228 can be a pure conductive coating, for example, the first conductive part 228 is a pure conductive coating composed of an adhesive and a conductive agent; the first conductive part 228 can also be an active coating containing lithium ions layer, for example, the first conductive part 228 is an active coating containing lithium ions composed of a lithium-rich material, a binder and a conductive agent; the first conductive part 228 can also be an inactive coating containing lithium ions, for example, The first conductive part 228 is a lithium ion-containing inactive coating composed of a binder, a conductive agent and lithium powder coated with lithium carbonate.
  • the second active material portion 2243 may also be connected between the first conductive portion 228 and the first inner surface 2241a of the first current collecting portion 2241, and the first active material portion 2242 The thickness is equal to or greater than the total thickness of the second active material portion 2243 and the first conductive portion 228 .
  • the active material capacity per unit area outside the first bending portion 224 may be greater than the active material capacity per unit area inside the first bending portion 224 by other means, for example, the first active material portion 2242
  • the thickness is equal to the thickness of the second active material portion 2243, and the gram capacity of the active material in the first active material portion 2242 is greater than the gram capacity of the active material in the second active material portion 2243, so as to realize the outer side of the first bending portion 224.
  • the capacity of active material per unit area is larger than the capacity of active material per unit area inside the first bent portion 224 .
  • the gram capacity refers to the ratio of the capacitance released by the active material to the mass of the active material.
  • the active material of the first active material portion 2242 is different from the active material of the second active material portion 2243.
  • the active material of the first active material portion 2242 is silicon
  • the active material of the second active material portion 2243 is graphite.
  • the gram capacity of the active material in the first active material part 2242 is 0.5%-20% greater than the gram capacity of the active material in the second active material part 2243 .
  • the gram capacity of the active material in the first active material portion 2242 is 1.5%-12% greater than the gram capacity of the active material in the second active material portion 2243 .
  • the active material capacity per unit area outside the first bending portion 224 may be greater than the active material capacity per unit area inside the first bending portion 224 by other means.
  • the first active material portion 2242 The thickness is equal to the thickness of the second active material portion 2243, the active material in the first active material portion 2242 is the same as the active material in the second active material portion 2243, and the proportion of the active material in the first active material portion 2242 is larger than that of the second active material portion 2242.
  • the ratio of the active material in the two active material portion 2243 is equal to the thickness of the second active material portion 2243, the active material in the first active material portion 2242 is the same as the active material in the second active material portion 2243, and the proportion of the active material in the first active material portion 2242 is larger than that of the second active material portion 2242.
  • the ratio of the active material in the two active material portion 2243 is the ratio of the active material in the two active material portion 2243 .
  • the active material capacity per unit area outside the third bending portion 226 can be equal to the active material capacity per unit area inside the third bending portion 226 in various ways.
  • the material of the fifth active material portion 2262 in the third bending portion 226 is the same as that of the sixth active material portion 2263
  • the thickness of the fifth active material portion 2262 is equal to the thickness of the fifth active material portion 2262 .
  • FIG. 10 is a partial enlarged view of a portion of the electrode assembly 22 located in the bending region B according to further embodiments of the present application.
  • At least one bending portion 223 in the positive electrode piece 221 is a In the second bent portion 225 , the capacity per unit area of the active material outside the second bent portion 225 is greater than the capacity per unit area of the active material inside the second bent portion 225 .
  • the bent portion 223 adjacent to the second bent portion 225 is the fourth bent portion 227 , and the active material capacity per unit area outside the fourth bent portion 227 is equal to the unit inside the fourth bent portion 227 Area active material capacity.
  • the active material capacity per unit area outside the second bending portion 225 is greater than the active material capacity per unit area inside the second bending portion 225
  • the active material capacity per unit area outside the fourth bending portion 227 may be equal to the fourth bending portion 227 .
  • the capacity of the active material per unit area inside the folded portion 227 is to simplify the manufacturing process of the negative pole piece 220 .
  • the second bending portion 225 includes a second current collecting portion 2251 , a third active material portion 2252 and a fourth active material portion 2253 .
  • the second current collecting portion 2251 has a second inner surface 2251a and a second outer surface 2251b arranged opposite to each other in the thickness direction thereof, the third active material portion 2252 is provided on the second outer surface 2251b, and the fourth active material portion 2253 is provided on the second outer surface 2251b.
  • the fourth bent portion 227 includes a fourth current collecting portion 2271 , a seventh active material portion 2272 and an eighth active material portion 2273 .
  • the fourth current collecting part 2271 has a fourth inner surface 2271a and a fourth outer surface 2271b arranged opposite to each other in the thickness direction, the seventh active material part 2272 is provided on the fourth outer surface 2271b, and the eighth active material part 2273 is provided on the fourth outer surface 2271b.
  • the second current collector portion 2251 is a layer of the positive electrode current collector 2211 (see FIG. 7 ) in the bending region B
  • the third active material portion 2252 is the first positive electrode active material layer 2212 (see FIG. 7 ) in the bending region.
  • the fourth active material portion 2253 is a layer of the second positive electrode active material layer 2213 (see FIG. 7 ) in the bending region B.
  • the fourth current collecting part 2271 is a layer of the negative electrode current collector 2201 (see FIG. 7 ) in the bending area B
  • the seventh active material part 2272 is the first negative electrode active material layer 2202 (see FIG. 7 ) in the bending area B.
  • the eighth active material portion 2273 is a layer of the second negative electrode active material layer 2203 (see FIG. 7 ) in the bending region B.
  • the active material capacity per unit area outside the second bent portion 225 is larger than the active material capacity per unit area inside the second bent portion 225 , that is, the activity per unit area of the third active material portion 2252 (outer portion of the second bent portion 225 ).
  • the material capacity is larger than the active material capacity per unit area of the fourth active material portion 2253 (the inner portion of the second bent portion 225 ).
  • the active material capacity per unit area outside the second bent portion 225 may be the ratio of the active material capacity of the third active material portion 2252 to the area of the second outer surface 2251b, and the active material capacity per unit area inside the second bent portion 225 may be is the ratio of the active material capacity of the fourth active material portion 2253 to the area of the second inner surface 2251a.
  • the active material capacity per unit area outside the fourth bent portion 227 is equal to the active material capacity per unit area inside the fourth bent portion 227 , that is, the activity per unit area of the seventh active material portion 2272 (outer portion of the fourth bent portion 227 ).
  • the material capacity is equal to the active material capacity per unit area of the eighth active material portion 2273 (the inner portion of the fourth bent portion 227 ).
  • the active material capacity per unit area outside the fourth bent portion 227 may be the ratio of the active material capacity of the seventh active material portion 2272 to the area of the fourth outer surface 2271b, and the active material capacity per unit area inside the fourth bent portion 227 may be is the ratio of the active material capacity of the eighth active material portion 2273 to the area of the fourth inner surface 2271a.
  • all the bent portions 223 may be the second bent portions 225 , or some of the bent portions 223 may be the second bent portions 225 . If all the bent portions 223 in the positive electrode sheet 221 are the second bent portions 225 , the active material capacity per unit area outside all the bent portions 223 in the positive electrode sheet 221 is larger than the inner active material capacity. If only part of the bent portion 223 of the positive electrode piece 221 is the second bent portion 225, all the bent portions 223 of the positive electrode piece 221 except the second bent portion 225 can be made of the one whose capacity per unit area of the active material on the outside is equal to that on the inside. The structure of the active material capacity per unit area. In the negative pole piece 220 , all the bent portions 223 may be the fourth bent portions 227 , or only part of the bent portions 223 may be the fourth bent portions 227 .
  • some of the bent portions 223 in the positive electrode piece 221 are the second bent portions 225 , and all the bent portions 223 in the negative electrode sheet 220 are the fourth bent portions 227 .
  • the positive pole piece 221 may be one or more bending parts 223 at the innermost side of the bending region B as the second bending parts 225 .
  • the two innermost bending parts 223 in the positive pole piece 221 are the second bending parts 225 .
  • all the bent portions 223 in the positive pole piece 221 are the second bent portions 225
  • all the bent portions 223 in the negative pole piece 220 are the fourth bent portions 227 .
  • each negative active material layer may be distributed on the negative current collector 2201 with equal thickness along the winding direction A; in the positive pole piece 221, each positive active material layer may be distributed along the winding direction A along The winding direction A is distributed in the positive electrode current collector 2211 with the same thickness.
  • the active material capacity per unit area outside the second bending portion 225 may be greater than the active material capacity per unit area inside the second bending portion 225 in various ways.
  • the material of the third active material portion 2252 in the second bending portion 225 is the same as the material of the fourth active material portion 2253 , and the thickness of the third active material portion 2252 is greater than that of the fourth active material portion 2252 .
  • the thickness of the active material portion 2253 is the same as the material of the fourth active material portion 2253 .
  • the thickness of the third active material part 2252 is greater than the thickness of the fourth active material part 2253, so that the thickness of the third active material part 2252
  • the active material capacity per unit area is greater than that of the fourth active material portion 2253 , so that the active material capacity per unit area outside the second bending portion 225 is greater than the active material capacity per unit area inside the second bending portion 225 .
  • the material of the third active material part 2252 is the same as the material of the fourth active material part 2253 , that is, the second inner surface 2251 a and the second outer surface 2251 b of the second current collecting part 2251 are coated with the same active material Department of Matter. It can be understood that the components of the third active material part 2252 are the same as the components of the fourth active material part 2253 , and the proportion of each component of the third active material part 2252 is the same as that of the fourth active material part 2253 .
  • the third active material part 2252 and the fourth active material part 2253 both include active materials, conductive agents and adhesives.
  • the proportion of the material is the same, the proportion of the conductive agent in the third active material part 2252 is the same as the proportion of the conductive agent in the fourth active material part 2253, and the proportion of the adhesive in the third active material part 2252 is the same as that in the fourth active material part 2253.
  • the proportion of the adhesive in the fourth active material portion 2253 is the same.
  • the thickness of the third active material portion 2252 is greater than that of the fourth active material portion 2253 by 0.5%-20%.
  • the thickness of the third active material portion 2252 is greater than that of the fourth active material portion 2253 by 1.5%-12%.
  • one or more bending parts 223 of the positive electrode piece 221 at the innermost part of the bending area B are the second bending parts 225 , it may be the first positive active material in one or more turns of the innermost circle of the positive electrode piece 221 .
  • the thickness of the layer 2212 is greater than the thickness of the second positive electrode active material layer 2213 . Taking the two innermost bending parts 223 of the positive electrode piece 221 in the bending area B as the second bending parts 225 as an example, the two innermost circles of the first positive electrode active material layer 2212 of the positive electrode electrode piece 221 can be used as an example.
  • the thickness is greater than the thickness of the second positive electrode active material layer 2213, so that the thickness of the third active material portion 2252 of the second bending portion 225 is greater than the thickness of the fourth active material portion 2253, so that the two innermost circles of the positive electrode plate 221
  • the second bending portion 225 is less prone to lithium deposition, which not only improves the safety of the battery cell 20 but also improves the energy density of the battery cell 20 .
  • FIG. 11 is a partial enlarged view of a portion of the electrode assembly 22 located in the bending region B according to other embodiments of the present application.
  • the second bending portion 225 further includes a second conductive portion 229 , the second conductive portion 229 is connected between the fourth active material portion 2253 and the second inner surface 2251a of the second current collecting portion 2251, and the thickness of the third active material portion 2252 is equal to or greater than that of the fourth active material portion 2253 and the second The total thickness of the conductive portion 229 .
  • the thickness of the third active material portion 2252 is equal to or greater than that of the fourth active material portion 2253 and the second conductive portion 2252.
  • the total thickness of the portion 229 is adjusted so that the thickness of the third active material portion 2252 is greater than that of the fourth active material portion 2253 .
  • the thickness of the third active material portion 2252 can be realized as follows: larger than the thickness of the fourth active material portion 2253 .
  • the second conductive part 229 can be a pure conductive coating, for example, the second conductive part 229 is a pure conductive coating composed of an adhesive and a conductive agent; the second conductive part 229 can also be an active coating containing lithium ions layer, for example, the second conductive part 229 is an active coating containing lithium ions composed of a lithium-rich material, a binder and a conductive agent; the second conductive part 229 can also be an inactive coating containing lithium ions, for example, The second conductive portion 229 is a lithium ion-containing inactive coating composed of a binder, a conductive agent, and lithium powder coated with lithium carbonate.
  • the fourth active material part 2253 may also be connected between the second conductive part 229 and the second inner surface 2251a of the second current collecting part 2251, and the third active material part 2252 The thickness is equal to or greater than the total thickness of the fourth active material portion 2253 and the second conductive portion 229 .
  • the active material capacity per unit area outside the second bending portion 225 may be greater than the active material capacity per unit area inside the second bending portion 225 by other means, for example, the capacity of the third active material portion 2252
  • the thickness is equal to the thickness of the fourth active material portion 2253, and the gram capacity of the active material in the third active material portion 2252 is greater than the gram capacity of the active material in the fourth active material portion 2253, so as to realize the outer side of the second bending portion 225.
  • the capacity of the active material per unit area is larger than the capacity of the active material per unit area inside the second bent portion 225 .
  • the active material of the third active material part 2252 may be different from the active material of the fourth active material part 2253.
  • the active material of the third active material part 2252 is ternary lithium
  • the fourth active material part The active material in 2253 is lithium iron phosphate.
  • the gram capacity of the active material in the third active material part 2252 is 0.5%-20% larger than the gram capacity of the active material in the fourth active material part 2253 .
  • the gram capacity of the active material in the third active material portion 2252 is 1.5%-12% greater than the gram capacity of the active material in the fourth active material portion 2253 .
  • the active material capacity per unit area outside the second bending portion 225 may be greater than the active material capacity per unit area inside the second bending portion 225 by other means.
  • the third active material portion 2252 The thickness is equal to the thickness of the fourth active material portion 2253, the active material in the third active material portion 2252 is the same as the active material in the fourth active material portion 2253, and the proportion of the active material in the third active material portion 2252 is larger than that in the third active material portion 2252.
  • the ratio of the active material in the four active material portion 2253 is the ratio of the active material in the four active material portion 2253 .
  • the active material capacity per unit area outside the fourth bending portion 227 can be equal to the active material capacity per unit area inside the fourth bending portion 227 in various ways.
  • the material of the seventh active material portion 2272 in the fourth bending portion 227 is the same as the material of the eighth active material portion 2273
  • the thickness of the seventh active material portion 2272 is equal to the thickness of the eighth active material portion 2273 .
  • FIG. 12 is a partial enlarged view of a portion of the electrode assembly 22 located in the bending region B according to further embodiments of the present application.
  • At least one bending portion 223 of the negative electrode piece 220 is a In the first bent portion 224, the active material capacity per unit area outside the first bent portion 224 is greater than the active material capacity per unit area inside the first bent portion 224;
  • at least one bent portion 223 in the positive electrode piece 221 is the second In the bent portion 225 , the active material capacity per unit area outside the second bent portion 225 is larger than the active material capacity per unit area inside the second bent portion 225 .
  • the thickness of the first active material part 2242 of the first bending part 224 can be made larger than the thickness of the second active material part 2243 , or the thickness of the first active material part 2242 of the first bending part 224 can be The gram capacity of the active material is greater than the gram capacity of the active material of the second active material part 2243, etc., so that the active material capacity per unit area outside the first bending part 224 is larger than the active material capacity per unit area inside the first bending part 224 Similarly, the thickness of the third active material part 2252 of the second bending part 225 can be made larger than the thickness of the fourth active material part 2253, or by making the active material of the third active material part 2252 of the second bending part 225 larger The gram capacity of the fourth active material portion 2253 is greater than that of the active material of the fourth active material portion 2253 , so that the active material capacity per unit area outside the second bending portion 225 is greater than the active material capacity per unit area inside the second bending portion 225 .
  • the material of the first active material part 2242 of the first bending part 224 is the same as the material of the second active material part 2243 , and the thickness of the first active material part 2242 of the first bending part 224 greater than the thickness of the second active material portion 2243; the material of the third active material portion 2252 of the second bending portion 225 is the same as the material of the fourth active material portion 2253, and the material of the third active material portion 2252 of the second bending portion 225 The thickness is larger than the thickness of the fourth active material portion 2253 .
  • a second bending part 225 adjacent to the first bending part 224 is arranged on the outer side of the first bending part 224 .
  • the capacity of active material per unit area outside the first bent portion 224 is greater than that of the first bent portion
  • the active material capacity per unit area inside the second bending part 225 is larger than the active material capacity per unit area inside the second bending part 225, which can increase the capacity of the outer part of the first bending part 224. CB value, thereby reducing the occurrence of lithium precipitation.
  • all the bent portions 223 may be the first bent portions 224 , or some of the bent portions 223 may be the first bent portions 224 .
  • all the bent portions 223 may be the second bent portions 225 , or some of the bent portions 223 may be the second bent portions 225 .
  • a portion of the bent portion 223 in the negative pole piece 220 is a first bent portion 224
  • a portion of the bent portion 223 in the positive electrode piece 221 is a second bent portion 225 .
  • the negative pole piece 220 may have one or more bending portions 223 at the innermost side of the bending region B as the first bending portion 224 .
  • the two innermost bending parts 223 in the negative pole piece 220 are the first bending parts 224 .
  • the positive pole piece 221 may have one or more bending portions 223 at the innermost side of the bending region B as the second bending portion 225 .
  • the two innermost bending parts 223 in the positive pole piece 221 are the second bending parts 225 .
  • all the bent portions 223 in the negative pole piece 220 are the first bent portions 224
  • all the bent portions 223 in the positive pole piece 221 are the second bent portions 225 .
  • each negative active material layer may be distributed on the negative electrode current collector 2201 with equal thickness along the winding direction A (see FIG. 7); in the positive pole piece 221, each negative electrode active material layer may The positive electrode active material layer is distributed in the positive electrode current collector 2211 with the same thickness along the winding direction A (see FIG. 7 ).
  • All the bent parts 223 in the negative electrode piece 220 are the first bent parts 224.
  • the active material per unit area outside the first bent part 224 The capacity is greater than the capacity of the active material per unit area inside the first bent portion 224 , which is equivalent to increasing the capacity of the active material per unit area outside the first bent portion 224 , so that the outer portion of all the bent portions 223 in the negative pole piece 220 is increased.
  • the CB value of both increases, and the part of the negative pole piece 220 located in the bending region B is not prone to lithium deposition.
  • All the bent parts 223 in the positive electrode sheet 221 are the second bent parts 225.
  • the active material per unit area outside the second bent part 225 meets the design requirements, the active material per unit area outside the second bent part 225 The capacity is greater than the capacity of the active material per unit area inside the second bending portion 225 , which is equivalent to reducing the active material capacity per unit area inside the second bending portion 225 , so that the outer sides of the plurality of bending portions 223 in the negative pole piece 220 are reduced. Part of the CB value increases, and the part of the negative pole piece 220 located in the bending region B is less likely to cause lithium precipitation.
  • FIG. 13 is a flowchart of a method for manufacturing the electrode assembly 22 provided by some embodiments of the present application.
  • the method for manufacturing the electrode assembly 22 includes:
  • the winding structure includes a bending area B, and both the negative pole piece 220 and the positive pole piece 221 include a plurality of bending parts 223 located in the bending area B.
  • At least one bent portion 223 in the negative pole piece 220 is a first bent portion 224, and the active material capacity per unit area outside the first bent portion 224 is greater than the active material capacity per unit area inside the first bent portion 224; and/ Alternatively, at least one bent portion 223 in the positive electrode sheet 221 is the second bent portion 225 , and the active material capacity per unit area outside the second bent portion 225 is greater than the active material capacity per unit area inside the second bent portion 225 .
  • a separator 222 for separating the positive pole piece 221 and the negative pole piece 220 is also provided, and the first pole piece, the separator 222 and the second pole piece are wound along the winding direction A to form a roll around the structure.
  • FIG. 14 is a schematic block diagram of a manufacturing equipment 2000 of an electrode assembly 22 provided by some embodiments of the present application.
  • the manufacturing equipment 2000 includes a providing device 2100 and an assembling device 2200 , and the providing device 2100 is used to provide the negative pole piece 220 and For the positive pole piece 221, the assembly device 2200 is used for winding the negative pole piece 220 and the positive pole piece 221 along the winding direction A to form a winding structure.
  • the winding structure includes a bending area B, and both the negative pole piece 220 and the positive pole piece 221 include a plurality of bending parts 223 located in the bending area B.
  • At least one bent portion 223 in the negative pole piece 220 is a first bent portion 224, and the active material capacity per unit area outside the first bent portion 224 is greater than the active material capacity per unit area inside the first bent portion 224; and/ Alternatively, at least one bent portion 223 in the positive electrode sheet 221 is the second bent portion 225 , and the active material capacity per unit area outside the second bent portion 225 is greater than the active material capacity per unit area inside the second bent portion 225 .
  • the providing device 2100 is further configured to provide a separator 222 for isolating the positive pole piece 221 and the negative pole piece 220 .
  • the assembling device 2200 is used for winding the first pole piece, the isolation film 222 and the second pole piece along the winding direction A to form a winding structure.
  • the embodiment of the present application also provides a CB value testing method of the electrode assembly 22, and the CB value testing steps are as follows:
  • Step 1) Average discharge capacity test of the single-sided active material layer of the positive electrode. Take the positive pole pieces 221 of the above-mentioned embodiments, and use a punching die to obtain a small round piece containing a positive electrode single-sided active material layer. Using lithium metal sheet as the counter electrode, Celgard film as the separator, EC+DMC+DEC dissolved with LiPF6 (1mol/L) (ethylene carbonate, dimethyl carbonate, diethyl carbonate with a volume ratio of 1:1:1) The solution of ester) was the electrolyte, and 6 identical CR2430 button cells were assembled in an argon-protected glove box.
  • LiPF6 (1mol/L)
  • the positive electrode active material is lithium iron phosphate (LFP)
  • the upper limit cut-off voltage x1V 3.75V
  • the lower limit cut-off voltage y1V 2V
  • the positive electrode active material is lithium nickel cobalt manganese oxide (NCM)
  • the upper limit cut-off voltage x1V 4.25V
  • the lower limit cut-off voltage y1V 2.8V.
  • Step 2) Average charge capacity test of the single-sided active material layer of the negative electrode. Take the negative electrode pole piece 220 of each of the above embodiments, and use a punching die to obtain a small round piece with the same area as the positive electrode small round piece in the above step 1) and including a negative electrode single film layer. Using lithium metal sheet as the counter electrode, Celgard film as the separator, EC+DMC+DEC dissolved with LiPF6 (1mol/L) (ethylene carbonate, dimethyl carbonate, diethyl carbonate with a volume ratio of 1:1:1) The solution of ester) was the electrolyte, and six CR2430 button cells were assembled in an argon-protected glove box.

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Abstract

本申请实施例提供了一种电极组件、电池单体、电池及电极组件的制造设备和方法，属于电池技术领域。电极组件包括负极极片和正极极片，负极极片和正极极片沿卷绕方向卷绕并形成卷绕结构，卷绕结构包括弯折区。负极极片和正极极片均包括位于弯折区的多个弯折部。负极极片中的至少一个弯折部为第一弯折部，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量；和/或，正极极片中的至少一个弯折部为第二弯折部，第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。这种结构的电极组件中极片在弯折区的至少部分区域的活性物质布置更为合理，具有更好的经济性。

Description

电极组件、电池单体、电池及电极组件的制造设备和方法 技术领域
本申请涉及电池技术领域，具体而言，涉及一种电极组件、电池单体、电池及电极组件的制造设备和方法。
背景技术
目前，车辆使用较多的电池一般是锂离子电池，锂离子电池作为一种可再充电电池，具有体积小、能量密度高、功率密度高、循环使用次数多和存储时间长等优点。
可再充电电池一般包括壳体和电极组件，壳体用于容纳电极组件和电解液，电极组件一般包括正极极片和负极极片，通过金属离子(如锂离子)在正极极片和负极极片之间移动来产生电能。
对于一般的电极组件而言，极片中的活性物质布置不合理，经济性较差。
发明内容
本申请实施例提供一种电极组件、电池单体、电池及电极组件的制造设备和方法，以改善极片中的活性物质布置不合理的问题。
第一方面，本申请实施例提供一种电极组件，包括负极极片和正极极片，所述负极极片和所述正极极片沿卷绕方向卷绕并形成卷绕结构，所述卷绕结构包括弯折区；所述负极极片和所述正极极片均包括位于所述弯折区的多个弯折部；其中，所述负极极片中的至少一个弯折部为第一弯折部，所述第一弯折部外侧的单位面积活性物质容量大于所述第一弯折部内侧的单位面积活性物质容量；和/或，所述正极极片中的至少一个弯折部为第二弯折部，所述第二弯折部外侧的单位面积活性物质容量大于所述第二弯折部内侧的单位面积活性物质容量。
上述方案中，负极极片的第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量，不易出现第一弯折部的内侧活性物质过剩，而第一弯折部的外侧活性物质不足的情况，使得负极极片至少部分区域(第一弯折部所在的区域)的活性物质布置更为合理；正极极片的第二弯折部外侧的单位活性物质容量大于第二弯折部内侧的单位面积活性物质容量，不易出现第二弯折部的外侧活性物质不足，而第二弯折部的内侧活性物质过剩的情况，使得正极极片至少部分区域(第二弯折部所在的区域)的活性物质布置更为合理。这种结构的电极组件中极片的至少部分区域的活 性物质布置更为合理，具有更好的经济性。
在一些实施例中，所述负极极片中的至少一个弯折部为所述第一弯折部，所述正极极片中的至少一个弯折部为所述第二弯折部，所述第一弯折部的外侧布置有与所述第一弯折部相邻的所述第二弯折部。
上述方案中，第一弯折部的外侧布置有与第一弯折部相邻的第二弯折部，在第一弯折部内侧单位面积活性物质容量和第二弯折部外侧单位面积活性物质容量满足设计要求时，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量，第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量，可增大第一弯折部的外侧部分的CB值，从而降低析锂现象的发生。
在一些实施例中，所述负极极片中的至少一个弯折部为所述第一弯折部；所述正极极片中与所述第一弯折部相邻的弯折部为第三弯折部；所述第三弯折部外侧的单位面积活性物质容量等于所述第三弯折部内侧的单位面积活性物质容量。
上述方案中，正极极片中与第一弯折部相邻的弯折部为第三弯折部，在第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量的情况下，第三弯折部外侧的单位面积活性物质容量可以等于第三弯折部内侧的单位面积活性物质容量，可简化正极极片的制造工艺。
在一些实施例中，所述正极极片中的至少一个弯折部为所述第二弯折部；所述负极极片中与所述第二弯折部相邻的弯折部为第四弯折部；所述第四弯折部外侧的单位面积活性物质容量等于所述第四弯折部内侧的单位面积活性物质容量。
上述方案中，负极极片中与第二弯折部相邻的弯折部为第四弯折部，在第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量的情况下，第四弯折部外侧的单位面积活性物质容量可以等于第四弯折部内侧的单位面积活性物质容量，可简化负极极片的制造工艺。
在一些实施例中，所述第一弯折部包括第一集流部、第一活性物质部和第二活性物质部；所述第一集流部在其厚度方向上具有相对布置的第一内表面和第一外表面，所述第一活性物质部设于所述第一外表面，所述第二活性物质部设于所述第一内表面。
在一些实施例中，所述第二活性物质部的材料与所述第一活性物质部的材料相同；所述第一活性物质部的厚度大于所述第二活性物质部的厚度。
上述方案中，在第一活性物质部的材料与第二活性物质部的材料相同的情况下，第一活性物质部的厚度大于第二活性物质部的厚度，可使得第一活性物质部的单位面积活性物质容量大于第二活性物质部的单位面积活性物质容量，从而实现第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量。
在一些实施例中，所述第一弯折部还包括第一导电部，所述第一导电部连接于所述第二活性物质部与所述第一内表面之间，所述第一活性物质部的厚度等于或大于所述第二活性物质部与所述第一导电部的总厚度。
上述方案中，通过在第二活性物质部与第一集流部之间设置第一导电部，使得第一活性物质部的厚度等于或大于第二活性物质部与第一导电部的总厚度，以实现第一活性物质部的厚度大于所述第二活性物质部的厚度。
在一些实施例中，所述第一活性物质部的厚度与所述第二活性物质部的厚度相等；所述第一活性物质部中的活性材料的克容量大于所述第二活性物质部中的活性材料的克容量。
上述方案中，在第一活性物质部的厚度与第二活性物质部的厚度相等的情况下，第一活性物质部中的活性材料的克容量大于第二活性物质部中的活性材料的克容量，可使得第一活性物质部的单位面积活性物质容量大于第二活性物质部的单位面积活性物质容量，从而实现第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量。
在一些实施例中，所述第二弯折部包括第二集流部、第三活性物质部和第四活性物质部；所述第二集流部在其厚度方向上具有相对布置的第二内表面和第二外表面，所述第三活性物质部设于所述第二外表面，所述第四活性物质部设于所述第二内表面。
在一些实施例中，所述第四活性物质部的材料与所述第三活性物质部的材料相同；所述第三活性物质部的厚度大于所述第四活性物质部的厚度。
上述方案中，在第三活性物质部的材料与第四活性物质部的材料相同的情况下，第三活性物质部的厚度大于所述第四活性物质部的厚度，可使得第三活性物质部的单位面积活性物质容量大于第四活性物质部的单位面积活性物质容量，从而实现第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。
在一些实施例中，所述第二弯折部还包括第二导电部，所述第二导电部连接于所述第四活性物质部与所述第二内表面之间，所述第三活性物质部的厚度等于或大于所述第四活性物质部与所述第二导电部的总厚度。
上述方案中，通过在第四活性物质部与第二集流部之间设置第二导电部，使得第三活性物质部的厚度等于或大于第四活性物质部与第二导电部的总厚度，以实现第三活性物质部的厚度大于所述第四活性物质部的厚度。
在一些实施例中，所述第三活性物质部的厚度与所述第四活性物质部的厚度相等；所述第三活性物质部中的活性材料的克容量大于所述第四活性物质部中的活性材料的克容量。
上述方案中，在第三活性物质部的厚度与第四活性物质部的厚度相等的情况下，第三活性物质部中的活性材料的克容量大于第四活性物质部中的 活性材料的克容量，可使得第三活性物质部的单位面积活性物质容量大于第四活性物质部的单位面积活性物质容量，从而实现第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。
在一些实施例中，所述负极极片包括负极集流体和设置于负极集流体厚度方向上的两侧的负极活性物质层；每个负极活性物质层沿所述卷绕方向等厚地分布于所述负极集流体。
上述方案中，每个负极活性物质层沿所述卷绕方向等厚地分布于正极集流体，可简化负极极片的制造工艺，有利于降低生产成本。
在一些实施例中，所述正极极片包括正极集流体和设置于正极集流体厚度方向上的两侧的正极活性物质层；每个正极活性物质层沿所述卷绕方向等厚地分布于所述正极集流体。
上述方案中，每个正极活性物质层沿所述卷绕方向等厚地分布于正极集流体，可简化正极极片的制造工艺，有利于降低生产成本。
在一些实施例中，所述负极极片中的全部弯折部均为所述第一弯折部。
上述方案中，负极极片中的全部弯折部均为第一弯折部，即负极极片中的全部弯折部均为外侧单位活性物质容量大于内侧的单位活性物质容量，使得负极极片中位于弯折区的部分的活性物质布置更为合理。在第一弯折部内侧单位面积活性物质容量满足设计要求时，由于第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量，相当于增大了第一弯折部外侧的单位面积活性物质容量，使得负极极片中的全部弯折部的外侧部分的CB值均增大，负极极片位于弯折区的部分不易发生析锂现象。
在一些实施例中，所述正极极片中的全部弯折部均为所述第二弯折部。
上述方案中，正极极片中的全部弯折部均为第二弯折部，即正极极片中的全部弯折部均为外侧单位活性物质容量大于内侧的单位活性物质容量，使得正极极片中位于弯折区的部分的活性物质布置更为合理。在第二弯折部外侧单位面积活性物质容量满足设计要求时，由于第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量，相当于减小了第二弯折部内侧的单位面积活性物质容量，使得负极极片中的多个弯折部的外侧部分的CB值均增大，负极极片位于弯折区的部分不易发生析锂现象。
第二方面，本申请实施例提供一种电池单体，包括外壳和上述第一方面任意一个实施例提供的电极组件；所述电极组件容纳于所述外壳内。
第三方面，本申请实施例提供一种电池，包括箱体和上述第二方面任 意一个实施例提供的电池单体；所述电池单体容纳于所述箱体内。
第四方面，本申请实施例提供一种用电设备，包括第二方面任意一个实施例提供的电池。
第五方面，本申请实施例提供一种电极组件的制造方法，包括：
提供正极极片和负极极片；将所述负极极片和所述正极极片沿卷绕方向卷绕并形成卷绕结构；其中，所述卷绕结构包括弯折区，所述负极极片和所述正极极片均包括位于所述弯折区的多个弯折部；所述负极极片中的至少一个弯折部为第一弯折部，所述第一弯折部外侧的单位面积活性物质容量大于所述第一弯折部内侧的单位面积活性物质容量；和/或，所述正极极片中的至少一个弯折部为第二弯折部，所述第二弯折部外侧的单位面积活性物质容量大于所述第二弯折部内侧的单位面积活性物质容量。
第六方面，本申请实施例还提供一种电极组件的制造设备，包括：提供装置，用于提供正极极片和负极极片；组装装置，用于将所述负极极片和所述正极极片沿卷绕方向卷绕并形成卷绕结构；其中，所述卷绕结构包括弯折区，所述负极极片和所述正极极片均包括位于所述弯折区的多个弯折部；所述负极极片中的至少一个弯折部为第一弯折部，所述第一弯折部外侧的单位面积活性物质容量大于所述第一弯折部内侧的单位面积活性物质容量；和/或，所述正极极片中的至少一个弯折部为第二弯折部，所述第二弯折部外侧的单位面积活性物质容量大于所述第二弯折部内侧的单位面积活性物质容量。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1为本申请一些实施例提供的车辆的结构示意图；
图2为本申请一些实施例提供的电池的爆炸图；
图3为图2所示的电池模块的结构示意图；
图4为图3所示的电池单体的爆炸图；
图5为本申请一些实施例提供的电极组件的结构示意图；
图6为本申请又一些实施例提供的电极组件的结构示意图；
图7为图5所示的电极组件的局部放大图；
图8为本申请一些实施例提供的电极组件位于弯折区的部分的局部放大图；
图9为本申请又一些实施例提供的电极组件位于弯折区的部分的局部放大图；
图10为本申请再一些实施例提供的电极组件位于弯折区的部分的局 部放大图；
图11为本申请另一些实施例提供的电极组件位于弯折区的部分的局部放大图；
图12为本申请又一些实施例提供的电极组件位于弯折区的部分的局部放大图；
图13为本申请一些实施例提供的电极组件的制造方法的流程图；
图14为本申请一些实施例提供的电极组件的制造设备的示意性框图。
在附图中，附图并未按照实际的比例绘制。
标记说明：10-箱体；11-第一部分；12-第二部分；13-容纳空间；20-电池单体；21-外壳；211-壳体；212-盖体；213-密封空间；214-正极电极端子；215-负极电极端子；216-泄压机构；22-电极组件；220-负极极片；2201-负极集流体；2202-第一负极活性物质层；2203-第二负极活性物质层；221-正极极片；2211-正极集流体；2212-第一正极活性物质层；2213-第二正极活性物质层；222-隔离膜；223-弯折部；224-第一弯折部；2241-第一集流部；2241a-第一内表面；2241b-第一外表面；2242-第一活性物质部；2243-第二活性物质部；225-第二弯折部；2251-第二集流部；2251a-第二内表面；2251b-第二外表面；2252-第三活性物质部；2253-第四活性物质部；226-第三弯折部；2261-第三集流部；2261a-第三内表面；2261b-第三外表面；2262-第五活性物质部；2263-第六活性物质部；227-第四弯折部；2271-第四集流部；2271a-第四内表面；2271b-第四外表面；2272-第七活性物质部；2273-第八活性物质部；228-第一导电部；229-第二导电部；30-电池模块；31-汇流部件；100-电池；200-控制器；300-马达；1000-车辆；2000-制造设备；2100-提供装置；2200-组装装置；A-卷绕方向；B-弯折区；C-平直区。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
除非另有定义，本申请所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本申请中在申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。本申请的说明书和权利要求书或上述附图中的术语“第一”、“第二”等是用于区别不同对象，而不是用于描述特定顺序或主次关系。
在本申请中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出 现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。
在本申请的描述中，需要说明的是，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”、“附接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
本申请中术语“和/或”，仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本申请中字符“/”，一般表示前后关联对象是一种“或”的关系。
在本申请的实施例中，相同的附图标记表示相同的部件，并且为了简洁，在不同实施例中，省略对相同部件的详细说明。应理解，附图示出的本申请实施例中的各种部件的厚度、长宽等尺寸，以及集成装置的整体厚度、长宽等尺寸仅为示例性说明，而不应对本申请构成任何限定。
本申请中出现的“多个”指的是两个以上(包括两个)。
本申请中，电池单体可以包括锂离子二次电池、锂离子一次电池、锂硫电池、钠锂离子电池、钠离子电池或镁离子电池等，本申请实施例对此并不限定。电池单体可呈圆柱体、扁平体、长方体或其它形状等，本申请实施例对此也不限定。电池单体一般按封装的方式分成三种：柱形电池单体、方形电池单体和软包电池单体，本申请实施例对此也不限定。
本申请的实施例所提到的电池是指包括一个或多个电池单体以提供更高的电压和容量的单一的物理模块。例如，本申请中所提到的电池可以包括电池模块或电池包等。电池一般包括用于封装一个或多个电池单体的箱体。箱体可以避免液体或其他异物影响电池单体的充电或放电。
电池单体包括电极组件和电解液，电极组件由正极片、负极片和隔离膜组成。电池单体主要依靠金属离子在正极片和负极片之间移动来工作。正极片包括正极集流体和正极活性物质层，正极活性物质层涂覆于正极集流体的表面，未涂敷正极活性物质层的正极集流体凸出于已涂覆正极活性物质层的正极集流体，未涂敷正极活性物质层的正极集流体作为正极极耳。以锂离子电池为例，正极集流体的材料可以为铝，正极活性物质可以为钴酸锂、磷酸铁锂、三元锂或锰酸锂等。负极片包括负极集流体和负极活性物质层，负极活性物质层涂覆于负极集流体的表面，未涂敷负极活性物质层的负极集流体凸出于已涂覆负极活性物质层的负极集流体，未涂敷负极活性物质层的负极集流体作为负极极耳。负极集流体的材料可以为铜，负极活性物质可以为碳或硅等。为了保证通过大电流而不发生熔断，正极极耳的数量为多个且层叠在一起，负极极耳的数量为多个且层叠在一起。隔离膜的材质可以为PP(polypropylene，聚丙烯)或PE(polyethylene，聚乙烯)等。此外，电极组件可以是卷绕式结构，也可以是叠片式结构，本申请实施例并不限于 此。
对于一般的电极组件而言，极片中的活性物质布置不合理，经济性较差。
发明人发现，电极组件中的负极极片的内侧活性物层厚度与负极极片的外侧活性物质层厚度等厚，负极极片的内侧活性物质层的材料与外侧活性物质层的材料相同；正极极片的内侧活性物质层厚度与正极极片的外侧活性物质层等厚，正极极片的内侧活性物质层的材料与外侧活性物质层的活性材料相同；在电极组件的弯折区内，负极极片的内侧活性物质层的半径大于位于负极极片内侧的正极极片的外侧活性物质层的半径，而负极极片的外侧活性物质层的半径会小于负极极片的外侧的正极极片的内侧活性物质层的半径，这样就会出现负极极片在弯折区内的弯折部的内侧活性物质过剩，外侧活性物质不足的情况，同样，也可能会出现正极极片在弯折区内的弯折部的外侧活性物质不足，而内侧活性物质过剩的情况。这种结构的电极组件，极片中的活性物质布置不合理，经济性较差。
鉴于此，本申请实施例提供一种技术方案，负极极片包括位于弯折区内的第一弯折部，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量，和/或，正极极片包括位于弯折区内的第二弯折部，第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。这种结构使得极片在弯折区的至少部分区域的活性物质布置更为合理，具有更好的经济性。
本申请实施例描述的技术方案适用于电池以及使用电池的用电设备。
用电设备可以是车辆、手机、便携式设备、笔记本电脑、轮船、航天器、电动玩具和电动工具等等。车辆可以是燃油汽车、燃气汽车或新能源汽车，新能源汽车可以是纯电动汽车、混合动力汽车或增程式汽车等；航天器包括飞机、火箭、航天飞机和宇宙飞船等等；电动玩具包括固定式或移动式的电动玩具，例如，游戏机、电动汽车玩具、电动轮船玩具和电动飞机玩具等等；电动工具包括金属切削电动工具、研磨电动工具、装配电动工具和铁道用电动工具，例如，电钻、电动砂轮机、电动扳手、电动螺丝刀、电锤、冲击电钻、混凝土振动器和电刨等等。本申请实施例对上述用电设备不做特殊限制。
以下实施例为了方便说明，以用电设备为车辆为例进行说明。
请参照图1，图1为本申请一些实施例提供的车辆1000的结构示意图，车辆1000的内部设置有电池100，电池100可以设置在车辆1000的底部或头部或尾部。电池100可以用于车辆1000的供电，例如，电池100可以作为车辆1000的操作电源。
车辆1000还可以包括控制器200和马达300，控制器200用来控制电池100为马达300供电，例如，用于车辆1000的启动、导航和行驶时的工作用电需求。
在本申请一些实施例中，电池100不仅仅可以作为车辆1000的操作 电源，还可以作为车辆1000的驱动电源，代替或部分地代替燃油或天然气为车辆1000提供驱动动力。
请参照图2，图2为本申请一些实施例提供的电池100的爆炸图，电池100包括箱体10和电池单体20(图2未示出)，电池单体20容纳于箱体10内。
箱体10用于容纳电池单体20，箱体10可以是多种结构。在一些实施例中，箱体10可以包括第一部分11和第二部分12，第一部分11与第二部分12相互盖合，第一部分11和第二部分12共同限定出用于容纳电池单体20的容纳空间13。可以是第二部分12为一端开口的空心结构，第一部分11为板状结构，第一部分11盖合于第二部分12的开口侧，以形成具有容纳空间13的箱体10；第一部分11和第二部分12也可以是均为一侧开口的空心结构，第一部分11的开口侧盖合于第二部分12的开口侧，以形成具有容纳空间13的箱体10。当然，第一部分11和第二部分12可以是多种形状，比如，圆柱体、长方体等。
为提高第一部分11与第二部分12连接后的密封性，第一部分11与第二部分12之间也可以设置密封件，比如，密封胶、密封圈等。
假设第一部分11盖合于第二部分12的顶部，第一部分11亦可称之为上盖，第二部分12亦可称之为下箱体。
在电池100中，电池单体20可以是一个，也可以是多个。若电池单体20为多个，多个电池单体20之间可串联或并联或混联，混联是指多个电池单体20中既有串联又有并联。多个电池单体20之间可直接串联或并联或混联在一起，再将多个电池单体20构成的整体容纳于箱体10内；当然，也可以是多个电池单体20先串联或并联或混联组成电池模块30，多个电池模块30再串联或并联或混联形成一个整体，并容纳于箱体10内。
在一些实施例中，请参照图3，图3为图2所示的电池模块30的结构示意图。电池单体20为多个，多个电池单体20先串联或并联或混联组成电池模块30。多个电池模块30再串联或并联或混联形成一个整体，并容纳于箱体10内。
电池模块30中的多个电池单体20之间可通过汇流部件31实现电连接，以实现电池模块30中的多个电池单体20的并联或串联或混联。
请参照图4，图4为图3所示的电池单体20的爆炸图。本申请实施例提供的电池单体20包括外壳21和电极组件22，电极组件22容纳于外壳21内。
在一些实施例中，外壳21还可用于容纳电解质，例如电解液。外壳21可以是多种结构形式。
在一些实施例中，外壳21可以包括壳体211和盖体212，壳体211为一侧开口的空心结构，盖体212盖合于壳体211的开口处并形成密封连接，以形成用于容纳电极组件22和电解质的密封空间213。
在组装电池单体20时，可先将电极组件22放入壳体211内，并向壳 体211内填充电解质，再将盖体212盖合于壳体211的开口。
壳体211可以是多种形状，比如，圆柱体、长方体等。壳体211的形状可根据电极组件22的具体形状来确定。比如，若电极组件22为圆柱体结构，则可选用为圆柱体壳体211；若电极组件22为长方体结构，则可选用长方体壳体211。当然，盖体212也可以是多种结构，比如，盖体212为板状结构、一端开口的空心结构等。示例性的，在图4中，壳体211为长方体结构，盖体212为板状结构，盖体212盖合于壳体211顶部的开口处。
在一些实施例中，电池单体20还可以包括正极电极端子214、负极电极端子215和泄压机构216，正极电极端子214、负极电极端子215和泄压机构216均安装于盖体212上。正极电极端子214和负极电极端子215均用于与电极组件22电连接，以输出电极组件22所产生的电能。泄压机构216用于在电池单体20的内部压力或温度达到预定值时泄放电池单体20内部的压力。
示例性的，泄压机构216位于正极电极端子214和负极电极端子215之间，泄压机构216可以是诸如防爆阀、防爆片、气阀、泄压阀或安全阀等部件。
当然，在一些实施例中，外壳21也可以是其他结构，比如，外壳21包括壳体211和两个盖体212，壳体211为相对的两侧开口的空心结构，一个盖体212对应盖合于壳体211的一个开口处并形成密封连接，以形成用于容纳电极组件22和电解质的密封空间213。在这种结构中，正极电极端子214和负极电极端子215可安装在同一个盖体212上，也可以安装在不同的盖体212上；可以是一个盖体212上安装有泄压机构216，也可以是两个盖体212上均安装有泄压机构216。
需要说明的是，在电池单体20中，容纳于外壳21内的电极组件22可以是一个，也可以是多个。示例性的，在图4中，电极组件22为两个。
接下来结合附图对电极组件22的具体结构进行详细阐述。
请参照图5，图5为本申请一些实施例提供的电极组件22的结构示意图，电极组件22包括负极极片220和正极极片221，负极极片220和正极极片221沿卷绕方向A卷绕并形成卷绕结构，卷绕结构包括弯折区B，负极极片220和正极极片221均包括位于弯折区B的多个弯折部223。
其中，负极极片220中的至少一个弯折部223为第一弯折部224(图5未示出)，第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量；和/或，正极极片221中的至少一个弯折部223为第二弯折部225(图5未示出)，第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量。
若负极极片220的第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量，不易出现第一弯折部224的内侧活性物质过剩，而第一弯折部224的外侧活性物质不足的情况，使得负极极片220至少部分区域(第一弯折部224所在的区域)的活性物质布置更 为合理。若正极极片221的第二弯折部225外侧的单位活性物质容量大于第二弯折部225内侧的单位面积活性物质容量，不易出现第二弯折部225的外侧活性物质不足，而第二弯折部225的内侧活性物质过剩的情况，使得正极极片221至少部分区域(第二弯折部225所在的区域)的活性物质布置更为合理。这种结构的电极组件22中极片的至少部分区域的活性物质布置更为合理，具有更好的经济性。
此外，在第一弯折部224内侧单位面积活性物质容量满足设计要求时，即第一弯折部224内侧单位面积活性物质容量达到第一预设值，使得第一弯折部224的内侧部分不易出现析锂，由于第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量，相对于第一预设值，相当于增大了第一弯折部224外侧的单位面积活性物质容量，可增大第一弯折部224的外侧部分的CB值，从而使得第一弯折部224的外侧部分不易出现析锂现象。同样，在第二弯折部225外侧单位面积活性物质容量满足设计要求时，即第二弯折部225外侧单位面积活性物质容量达到第二预设值，使得负极极片220位于第二弯折部225的外侧的弯折部223的内侧部分不易出现析锂，由于第二弯折部225外侧的单位活性物质容量大于第二弯折部225内侧的单位面积活性物质容量，相对于第二预设值，相当于减小了第二弯折部225内侧的单位面积活性物质容量，使得负极极片220位于第二弯折部225的内侧的弯折部223的外侧部分也不易出现析锂现象。
CB(Cell Balance)值为单位面积的负极活性物质的容量与单位面积的正极活性物质的容量的比值。负极极片220的弯折部223的外侧部分的CB(Cell Balance)值＝Q1/Q2，其中，负极极片220中的一个弯折部223的外侧活性物质的单位面积的活性物质容量为Q1，正极极片221中位于该一个弯折部223的外侧且与该一个弯折部223相邻的弯折部223的内侧活性物质的单位面积的活性物质容量为Q2。
在本申请实施例中，卷绕方向A即为正极极片221和负极极片220从内向外周向卷绕的方向。在图5中，卷绕方向A为顺时针方向。
在一些实施例中，电极组件22还可以包括隔离膜222，隔离膜222用于将正极极片221和负极极片220隔离，以降低正极极片221与负极极片220之间出现短路的风险。
隔离膜222的材质可以为PP(polypropylene，聚丙烯)或PE(polyethylene，聚乙烯)等。
在一些实施例中，如图5所示，卷绕结构还包括平直区C，平直区C与弯折区B相连，可以是平直区C相对的两端均设有弯折区B。平直区C即为卷绕结构具有平直结构的区域，正极极片221位于平直区C内的部分和负极极片220位于平直区C内的部分均基本平直布置。弯折区B即为卷绕结构具有弯折结构的区域，正极极片221位于弯折区B的部分(弯折部223)和负极极片220位于弯折区B的部分(弯折部223)均弯折分布。示例性的，正极极片221的弯折部223和负极极片220的弯折部223均至少部分为 圆弧形。
在本实施例中，卷绕结构包括平直区C和弯折区B，电极组件整体为扁平体。
需要说明的是，在弯折区B内布置有第一弯折部224的情况下，可以是只有一个弯折区B内布置有第一弯折部224，也可以是两个弯折区B内均布置有第一弯折部224；在弯折区B内布置有第二弯折部225的情况下，可以是只有一个弯折区B内布置有第二弯折部225，也可以是两个弯折区B内均布置有第二弯折部225。
示例性的，如图5所示，在弯折区B中，正极极片221中的多个弯折部223与负极极片220中的多个弯折部223交错排布，即在弯折区B中，以负极极片220的一个弯折部223、正极极片221的一个弯折部223、负极极片220的一个弯折部223……的顺序依次排布。
在其他实施例中，请参照图6，图6为本申请又一些实施例提供的电极组件22的结构示意图，卷绕结构中可以只有弯折区B，而没有平直区C，这种结构的电极组件22整体可以为圆柱体。在正极极片221中，正极极片221的一圈极片即为一个弯折部223；在负极极片220中，负极极片220的一圈极片即为一个弯折部223。
在一些实施例中，请参照图7，图7为图5所示的电极组件22的局部放大图，负极极片220包括负极集流体2201和设置于负极集流体2201厚度方向上的两侧的负极活性物质层，负极集流体2201厚度方向上的两侧的负极活性物质层分别为第一负极活性物质层2202和第二负极活性物质层2203，第一负极活性物质层2202设于负极集流体2201的外表面，第二负极活性物质层2203设于负极集流体2201的内表面。正极极片221包括正极集流体2211和设置于正极集流体2211厚度方向上的两侧的正极活性物质层，正极集流体2211厚度方向上的两侧的正极活性物质层分别为第一正极活性物质层2212和第二正极活性物质层2213，第一正极活性物质层2212设于正极集流体2211的外表面，第二正极活性物质层2213设于正极集流体2211的内表面。
其中，负极集流体2201可以具有未涂覆负极活性物质层的部分，该部分为负极极耳(图未示出)；正极集流体2211可以具有未涂覆负极活性物质层的部分，该部分为正极极耳(图未示出)。正极极耳用于与正极电极端子214(参见图4)电连接，负极极耳用于与负极电极端子215(参见图4)电连接。
在一些实施例中，在负极极片220中，每个负极活性物质层沿卷绕方向A等厚地分布于负极集流体2201，即第一负极活性物质层2202沿卷绕方向A等厚地分布于负极集流体2201，第二负极活性物质层2203沿卷绕方向A等厚地分布于负极集流体2201。这种结构可简化负极极片220的制造工艺，有利于降低生产成本。
可理解的，第一负极活性物质层2202位于弯折区B的每层的厚度 与第一负极活性物质层2202位于平直区C的每层的厚度相等；第二负极活性物质层2203位于弯折区B的每层的厚度与第二负极活性物质层2203位于平直区C的每层的厚度相等。
在一些实施例中，在正极极片221中，每个正极活性物质层沿卷绕方向A等厚地分布于正极集流体2211，即第一正极活性物质层2212沿卷绕方向A等厚地分布于正极集流体2211，第二正极活性物质层2213沿卷绕方向A等厚地分布于正极集流体2211。这种结构可简化正极极片221的制造工艺，有利于降低生产成本。
可理解的，第一正极活性物质层2212位于弯折区B的每层的厚度与第一正极活性物质层2212位于平直区C的每层的厚度相等；第二正极活性物质层2213位于弯折区B的每层的厚度与第二正极活性物质层2213位于平直区C的每层的厚度相等。
在一些实施例中，请参照图8，图8为本申请一些实施例提供的电极组件22位于弯折区B的部分的局部放大图，负极极片220中的至少一个弯折部223为第一弯折部224，负极极片220的第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量。正极极片221中与第一弯折部224相邻的弯折部223为第三弯折部226，第三弯折部226外侧的单位面积活性物质容量等于第三弯折部226内侧的单位面积活性物质容量。
在第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量的情况下，第三弯折部226外侧的单位面积活性物质容量可以等于第三弯折部226内侧的单位面积活性物质容量，以简化正极极片221的制造工艺。
其中，第一弯折部224包括第一集流部2241、第一活性物质部2242和第二活性物质部2243。第一集流部2241在其厚度方向上具有相对布置的第一内表面2241a和第一外表面2241b，第一活性物质部2242设于第一外表面2241b，第二活性物质部2243设于第一内表面2241a。第三弯折部226包括第三集流部2261、第五活性物质部2262和第六活性物质部2263。第三集流部2261在其厚度方向上具有相对布置的第三内表面2261a和第三外表面2261b，第五活性物质部2262设于第三外表面2261b，第六活性物质部2263设于第三内表面2261a。
可理解的，第一集流部2241为负极集流体2201(参见图7)在弯折区B的一层，第一活性物质部2242为第一负极活性物质层2202(参见图7)在弯折区B的一层，第二活性物质部2243为第二负极活性物质层2203(参见图7)在弯折区B的一层。第三集流部2261为正极集流体2211(参见图7)在弯折区B内的一层，第五活性物质部2262为第一正极活性物质层2212(参见图7)在弯折区B的一层，第六活性物质部2263为第二正极活性物质层2213(参见图7)在弯折区B的一层。
第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224 内侧的单位面积活性物质容量，即第一活性物质部2242(第一弯折部224的外侧部分)的单位面积活性物质容量大于第二活性物质部2243(第一弯折部224的内侧部分)的单位面积活性物质容量。第一弯折部224外侧的单位面积活性物质容量可以是第一活性物质部2242的活性材料容量与第一外表面2241b的面积的比值，第一弯折部224内侧的单位面积活性物质容量可以是第二活性物质部2243的活性材料容量与第一内表面2241a的面积的比值。
第三弯折部226外侧的单位面积活性物质容量等于第三弯折部226内侧的单位面积活性物质容量，即第五活性物质部2262(第三弯折部226的外侧部分)的单位面积活性物质容量等于第六活性物质部2263(第三弯折部226的内侧部分)的单位面积活性物质容量。第三弯折部226外侧的单位面积活性物质容量可以是第五活性物质部2262的活性材料容量与第三外表面2261b的面积的比值，第三弯折部226内侧的单位面积活性物质容量可以是第六活性物质部2263的活性材料容量与第三内表面2261a的比值。
在负极极片220中，可以是全部弯折部223为第一弯折部224，也可以是部分弯折部223为第一弯折部224。若负极极片220中的全部弯折部223为第一弯折部224，负极极片220中的全部弯折部223外侧的单位面活性物质容量大于内侧的单位面积活性物质容量。若负极极片220只有部分弯折部223为第一弯折部224，负极极片220中除了第一弯折部224以外的弯折部223均可以采用外侧的单位面积活性物质容量等于内侧的单位面积活性物质容量的结构。在正极极片221中，可以是全部弯折部223为第三弯折部226，也可以是只有部分弯折部223为第三弯折部226。
在一些实施例中，负极极片220中的部分弯折部223为第一弯折部224，正极极片221中的全部弯折部223为第三弯折部226。
其中，负极极片220中可以是在弯折区B最内侧的一个或多个弯折部223为第一弯折部224。示例性的，负极极片220中的最内侧的两个弯折部223为第一弯折部224。
在一些实施例中，负极极片220中的全部弯折部223为第一弯折部224，正极极片221中的全部弯折部223为第三弯折部226。
本实施例中，在负极极片220中，可以是每个负极活性物质层沿卷绕方向A等厚地分布于负极集流体2201；在正极极片221中，可以是每个正极活性物质层沿卷绕方向A等厚地分布于正极集流体2211。
在本申请实施例中，可通过多种方式来实现第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量。
在一些实施例中，请继续参照图8，第一弯折部224中的第一活性物质部2242的材料与第二活性物质部2243的材料相同，第一活性物质部2242的厚度大于第二活性物质部2243的厚度。
在第一活性物质部2242的材料与第二活性物质部2243的材料相同的情况下，第一活性物质部2242的厚度大于第二活性物质部2243的厚度，可使得第一活性物质部2242的单位面积活性物质容量大于第二活性物质部 2243的单位面积活性物质容量，从而实现第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量。
需要说明的是，第一活性物质部2242的材料与第二活性物质部2243的材料相同，即在第一集流部2241的第一内表面2241a和第一外表面2241b涂覆有相同的活性物质部。可理解的，第一活性物质部2242的成分与第二活性物质部2243的成分相同，且第一活性物质部2242的各成分比例与第二活性物质部2243的各成分比例相同。比如，第一活性物质部2242与第二活性物质部2243均包括活性材料、导电剂和粘接剂，第一活性物质部2242中的活性材料所占比例与第二活性物质部2243中的活性材料所占比例相同，第一活性物质部2242中的导电剂所占比例与第二活性物质部2243中的导电剂所占比例相同，第一活性物质部2242中的粘接剂所占比例与第二活性物质部2243中的粘接剂所占比例相同。
可选地，第一活性物质部2242的厚度比第二活性物质部2243的厚度大0.5％-20％。
示例性的，第一活性物质部2242的厚度比第二活性物质部2243的厚度大1.5％-12％。
若负极极片220在弯折区B最内侧的一个或多个弯折部223为第一弯折部224，可以是在负极极片220的最内一圈或多圈的第一负极活性物质层2202的厚度大于第二负极活性物质层2203的厚度。以负极极片220在弯折区B最内侧的两个弯折部223为第一弯折部224为例，可以是在负极极片220的最内两圈的第一负极活性物质层2202的厚度大于第二负极活性物质层2203的厚度，以使第一弯折部224的第一活性物质部2242的厚度大于第二活性物质部2243的厚度，使得负极极片220最内两圈的第一弯折部224不易出现析锂现象，既可提高电池单体20安全性，又可降低生产成本。
在一些实施例中，请参照图9，图9为本申请又一些实施例提供的电极组件22位于弯折区B的部分的局部放大图，第一弯折部224还包括第一导电部228，第一导电部228连接于第二活性物质部2243与第一集流部2241的第一内表面2241a之间，第一活性物质部2242的厚度等于或大于第二活性物质部2243与第一导电部228的总厚度。也就是说，通过在第二活性物质部2243与第一集流部2241之间设置第一导电部228，使得第一活性物质部2242的厚度等于或大于第二活性物质部2243与第一导电部228的总厚度，以实现第一活性物质部2242的厚度大于第二活性物质部2243的厚度。
在生产负极极片220时，只需使第一活性物质部2242的厚度等于或大于第二活性物质部2243与第一导电部228的总厚度，则可实现第一活性物质部2242的厚度则大于第二活性物质部2243的厚度。
其中，第一导电部228可以是纯导电涂层，比如，第一导电部228为由粘接剂和导电剂组成的纯导电涂层；第一导电部228也可以是含有锂离子的活性涂层，比如，第一导电部228为由富锂材料、粘接剂和导电剂组成 的含有锂离子的活性涂层；第一导电部228也可以是含锂离子的非活性涂层，比如，第一导电部228为由粘接剂、导电剂和被碳酸锂包覆的锂粉组成的含锂离子的非活性涂层。
需要说明的是，在其他实施例中，也可以是第二活性物质部2243连接于第一导电部228与第一集流部2241的第一内表面2241a之间，第一活性物质部2242的厚度等于或大于第二活性物质部2243与第一导电部228的总厚度。
在一些实施例中，也可通过其他方式来实现第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量，比如，第一活性物质部2242的厚度与第二活性物质部2243的厚度相等，第一活性物质部2242中的活性材料的克容量大于第二活性物质部2243中的活性材料的克容量，从而实现第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量。
克容量是指活性材料所释放出的电容量与活性材料的质量之比。
本实施例中，第一活性物质部2242的活性材料与第二活性物质部2243的活性材料不同，比如，第一活性物质部2242的活性材料为硅，第二活性物质部2243的活性材料为石墨。
可选地，第一活性物质部2242中的活性材料的克容量比第二活性物质部2243中的活性材料的克容量大0.5％-20％。
示例性的，第一活性物质部2242中的活性材料的克容量比第二活性物质部2243中的活性材料的克容量大1.5％-12％。
在其他实施例中，也可以通过其他方式来实现第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量，比如，第一活性物质部2242的厚度与第二活性物质部2243的厚度相等，第一活性物质部2242中的活性材料与第二活性物质部2243的活性材料相同，第一活性物质部2242中的活性材料所占的比例大于第二活性物质部2243中的活性材料所占的比例。
需要说明的是，在本申请实施例中，也可通过多种方式来实现第三弯折部226外侧的单位面积活性物质容量等于第三弯折部226内侧的单位面积活性物质容量。比如，第三弯折部226中的第五活性物质部2262的材料与第六活性物质部2263的材料相同，第五活性物质部2262的厚度等于第五活性物质部2262的厚度。
在一些实施例中，请参照图10，图10为本申请再一些实施例提供的电极组件22位于弯折区B的部分的局部放大图，正极极片221中的至少一个弯折部223为第二弯折部225，第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量。负极极片220中与第二弯折部225相邻的弯折部223为第四弯折部227，第四弯折部227外侧的单位面积活性物质容量等于第四弯折部227内侧的单位面积活性物质容量。
在第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量的情况下，第四弯折部227外侧的单位面积活性物质容量可以等于第四弯折部227内侧的单位面积活性物质容量，以简化负极极片220的制造工艺。
其中，第二弯折部225包括第二集流部2251、第三活性物质部2252和第四活性物质部2253。第二集流部2251在其厚度方向上具有相对布置的第二内表面2251a和第二外表面2251b，第三活性物质部2252设于第二外表面2251b，第四活性物质部2253设于第二内表面2251a。第四弯折部227包括第四集流部2271、第七活性物质部2272和第八活性物质部2273。第四集流部2271在其厚度方向上具有相对布置的第四内表面2271a和第四外表面2271b，第七活性物质部2272设于第四外表面2271b，第八活性物质部2273设于第四内表面2271a。
可理解的，第二集流部2251为正极集流体2211(参见图7)在弯折区B的一层，第三活性物质部2252为第一正极活性物质层2212(参见图7)在弯折区B的一层，第四活性物质部2253为第二正极活性物质层2213(参见图7)在弯折区B的一层。第四集流部2271为负极集流体2201(参见图7)在弯折区B内的一层，第七活性物质部2272为第一负极活性物质层2202(参见图7)在弯折区B的一层，第八活性物质部2273为第二负极活性物质层2203(参见图7)在弯折区B的一层。
第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量，即第三活性物质部2252(第二弯折部225的外侧部分)的单位面积活性物质容量大于第四活性物质部2253(第二弯折部225的内侧部分)的单位面积活性物质容量。第二弯折部225外侧的单位面积活性物质容量可以是第三活性物质部2252的活性材料容量与第二外表面2251b的面积的比值，第二弯折部225内侧的单位面积活性物质容量可以是第四活性物质部2253的活性材料容量与第二内表面2251a的面积的比值。
第四弯折部227外侧的单位面积活性物质容量等于第四弯折部227内侧的单位面积活性物质容量，即第七活性物质部2272(第四弯折部227的外侧部分)的单位面积活性物质容量等于第八活性物质部2273(第四弯折部227的内侧部分)的单位面积活性物质容量。第四弯折部227外侧的单位面积活性物质容量可以是第七活性物质部2272的活性材料容量与第四外表面2271b的面积的比值，第四弯折部227内侧的单位面积活性物质容量可以是第八活性物质部2273的活性材料容量与第四内表面2271a的面积的比值。
在正极极片221中，可以是全部弯折部223为第二弯折部225，也可以是部分弯折部223为第二弯折部225。若正极极片221中的全部弯折部223为第二弯折部225，正极极片221中的全部弯折部223外侧的单位面积活性物质容量大于内侧的单位面积活性物质容量。若正极极片221只有部分弯折部223为第二弯折部225，正极极片221中除了第二弯折部225以外的弯折部223均可以采用外侧的单位面积活性物质容量等于内侧的单位面积活 性物质容量的结构。在负极极片220中，可以是全部弯折部223为第四弯折部227，也可以是只有部分弯折部223为第四弯折部227。
在一些实施例中，正极极片221中的部分弯折部223为第二弯折部225，负极极片220中的全部弯折部223为第四弯折部227。
其中，正极极片221可以是在弯折区B最内侧的一个或多个弯折部223为第二弯折部225。示例性的，正极极片221中的最内侧的两个弯折部223为第二弯折部225。
在一些实施例中，正极极片221中的全部弯折部223为第二弯折部225，负极极片220中的全部弯折部223为第四弯折部227。
本实施例中，在负极极片220中，可以是每个负极活性物质层沿卷绕方向A等厚地分布于负极集流体2201；在正极极片221中，可以是每个正极活性物质层沿卷绕方向A等厚地分布于正极集流体2211。
在本申请实施例中，可通过多种方式来实现第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量。
在一些实施例中，请继续参照图10，第二弯折部225中的第三活性物质部2252的材料与第四活性物质部2253的材料相同，第三活性物质部2252的厚度大于第四活性物质部2253的厚度。
在第三活性物质部2252的材料与第四活性物质部2253的材料相同的情况下，第三活性物质部2252的厚度大于第四活性物质部2253的厚度，可使得第三活性物质部2252的单位面积活性物质容量大于第四活性物质部2253的单位面积活性物质容量，从而实现第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量。
需要说明的是，第三活性物质部2252的材料与第四活性物质部2253的材料相同，即在第二集流部2251的第二内表面2251a和第二外表面2251b涂覆有相同的活性物质部。可理解的，第三活性物质部2252的成分与第四活性物质部2253的成分相同，且第三活性物质部2252的各成分比例与第四活性物质部2253的各成分比例相同。比如，第三活性物质部2252与第四活性物质部2253均包括活性材料、导电剂和粘接剂，第三活性物质部2252中的活性材料所占比例与第四活性物质部2253中的活性材料所占比例相同，第三活性物质部2252中的导电剂所占比例与第四活性物质部2253中的导电剂所占比例相同，第三活性物质部2252中的粘接剂所占比例与第四活性物质部2253中的粘接剂所占比例相同。
可选地，第三活性物质部2252的厚度比第四活性物质部2253的厚度大0.5％-20％。
示例性的，第三活性物质部2252的厚度比第四活性物质部2253的厚度大1.5％-12％。
若正极极片221在弯折区B最内侧的一个或多个弯折部223为第二弯折部225，可以是在正极极片221的最内一圈或多圈的第一正极活性物质层2212的厚度大于第二正极活性物质层2213的厚度。以正极极片221在弯 折区B最内侧的两个弯折部223为第二弯折部225为例，可以是在正极极片221的最内两圈的第一正极活性物质层2212的厚度大于第二正极活性物质层2213的厚度，以使第二弯折部225的第三活性物质部2252的厚度大于第四活性物质部2253的厚度，使得正极极片221最内两圈的第二弯折部225不易出现析锂现象，既提高了电池单体20的安全性，又可提高电池单体20的能量密度。
在一些实施例中，请参照图11，图11为本申请另一些实施例提供的电极组件22位于弯折区B的部分的局部放大图，第二弯折部225还包括第二导电部229，第二导电部229连接于第四活性物质部2253与第二集流部2251的第二内表面2251a之间，第三活性物质部2252的厚度等于或大于第四活性物质部2253与第二导电部229的总厚度。也就是说，通过在第四活性物质部2253与第二集流部2251之间设置第二导电部229，使得第三活性物质部2252的厚度等于或大于第四活性物质部2253与第二导电部229的总厚度，以实现第三活性物质部2252的厚度大于第四活性物质部2253的厚度。
在生产正极极片221时，只需使第三活性物质部2252的厚度等于或大于第四活性物质部2253与第二导电部229的总厚度，则可实现第三活性物质部2252的厚度则大于第四活性物质部2253的厚度。
其中，第二导电部229可以是纯导电涂层，比如，第二导电部229为由粘接剂和导电剂组成的纯导电涂层；第二导电部229也可以是含有锂离子的活性涂层，比如，第二导电部229为由富锂材料、粘接剂和导电剂组成的含有锂离子的活性涂层；第二导电部229也可以是含锂离子的非活性涂层，比如，第二导电部229为由粘接剂、导电剂和被碳酸锂包覆的锂粉组成的含锂离子的非活性涂层。
需要说明的是，在其他实施例中，也可以是第四活性物质部2253连接于第二导电部229与第二集流部2251的第二内表面2251a之间，第三活性物质部2252的厚度等于或大于第四活性物质部2253与第二导电部229的总厚度。
在一些实施例中，也可通过其他方式来实现第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量，比如，第三活性物质部2252的厚度与第四活性物质部2253的厚度相等，第三活性物质部2252中的活性材料的克容量大于第四活性物质部2253中的活性材料的克容量，从而实现第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量。
本实施例中，可以是第三活性物质部2252的活性材料与第四活性物质部2253的活性材料不同，比如，第三活性物质部2252中的活性材质为三元锂，第四活性物质部2253中的活性材质为磷酸铁锂。
可选地，第三活性物质部2252中的活性材料的克容量比第四活性物质部2253中的活性材料的克容量大0.5％-20％。
示例性的，第三活性物质部2252中的活性材料的克容量比第四活性物质部2253中的活性材料的克容量大1.5％-12％。
在其他实施例中，也可以通过其他方式来实现第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量，比如，第三活性物质部2252的厚度与第四活性物质部2253的厚度相等，第三活性物质部2252中的活性材料与第四活性物质部2253的活性材料相同，第三活性物质部2252中的活性材料所占的比例大于第四活性物质部2253中的活性材料所占的比例。
需要说明的是，在本申请实施例中，也可通过多种方式来实现第四弯折部227外侧的单位面积活性物质容量等于第四弯折部227内侧的单位面积活性物质容量。比如，第四弯折部227中的第七活性物质部2272的材料与第八活性物质部2273的材料相同，第七活性物质部2272的厚度等于第八活性物质部2273的厚度。
在一些实施例中，请参照图12，图12为本申请又一些实施例提供的电极组件22位于弯折区B的部分的局部放大图，负极极片220中的至少一个弯折部223为第一弯折部224，第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量；正极极片221中的至少一个弯折部223为第二弯折部225，第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量。
在本实施例中，可以通过使第一弯折部224的第一活性物质部2242的厚度大于第二活性物质部2243的厚度，或通过使第一弯折部224的第一活性物质部2242的活性材料的克容量大于第二活性物质部2243的活性材料的克容量等方式，使得第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量；同样，可以通过使第二弯折部225的第三活性物质部2252的厚度大于第四活性物质部2253的厚度，或通过使第二弯折部225的第三活性物质部2252的活性材料的克容量大于第四活性物质部2253的活性材料的克容量等方式，使得第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量。
示例性的，在图112中，第一弯折部224的第一活性物质部2242的材料与第二活性物质部2243的材料相同，第一弯折部224的第一活性物质部2242的厚度大于第二活性物质部2243的厚度；第二弯折部225的第三活性物质部2252的材料与第四活性物质部2253的材料相同，第二弯折部225的第三活性物质部2252的厚度大于第四活性物质部2253的厚度。
在一些实施例中，第一弯折部224的外侧布置有与第一弯折部224相邻的第二弯折部225。
在第一弯折部224内侧单位面积活性物质容量和第二弯折部225外侧单位面积活性物质容量满足设计要求时，第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量，第二弯折 部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量，可增大第一弯折部224的外侧部分的CB值，从而降低析锂现象的发生。
在本实施例中，在负极极片220中，可以是全部弯折部223为第一弯折部224，也可以是部分弯折部223为第一弯折部224。在正极极片221中，可以是全部弯折部223为第二弯折部225，也可以是部分弯折部223为第二弯折部225。
在一些实施例中，负极极片220中的部分弯折部223为第一弯折部224，正极极片221中的部分弯折部223为第二弯折部225。
其中，负极极片220可以是在弯折区B最内侧的一个或多个弯折部223为第一弯折部224。示例性的，负极极片220中的最内侧的两个弯折部223为第一弯折部224。正极极片221可以是在弯折区B最内侧的一个或多个弯折部223为第二弯折部225。示例性的，正极极片221中的最内侧的两个弯折部223为第二弯折部225。
在一些实施例中，负极极片220中的全部弯折部223为第一弯折部224，正极极片221中的全部弯折部223为第二弯折部225。
本实施例中，在负极极片220中，可以是每个负极活性物质层沿卷绕方向A等厚地分布于负极集流体2201(参见图7)；在正极极片221中，可以是每个正极活性物质层沿卷绕方向A等厚地分布于正极集流体2211(参见图7)。
负极极片220中的全部弯折部223为第一弯折部224，在第一弯折部224内侧单位面积活性物质容量满足设计要求时，由于第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量，相当于增大了第一弯折部224外侧的单位面积活性物质容量，使得负极极片220中的全部弯折部223的外侧部分的CB值均增大，负极极片220位于弯折区B的部分不易发生析锂现象。正极极片221中的全部弯折部223为第二弯折部225，在第二弯折部225外侧单位面积活性物质容量满足设计要求时，由于第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量，相当于减小了第二弯折部225内侧的单位面积活性物质容量，使得负极极片220中的多个弯折部223的外侧部分的CB值均增大，负极极片220位于弯折区B的部分不易发生析锂现象。
请参照图13，图13为本申请一些实施例提供的电极组件22的制造方法的流程图，电极组件22的制造方法包括：
S100：提供负极极片220和正极极片221；
S200：将负极极片220和正极极片221沿卷绕方向A卷绕并形成卷绕结构；
其中，卷绕结构包括弯折区B，负极极片220和正极极片221均包括位于弯折区B的多个弯折部223。负极极片220中的至少一个弯折部223为第一弯折部224，第一弯折部224外侧的单位面积活性物质容量大于第一 弯折部224内侧的单位面积活性物质容量；和/或，正极极片221中的至少一个弯折部223为第二弯折部225，第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量。
在一些实施例中，还提供用于将正极极片221和负极极片220隔离的隔离膜222，将第一极片、隔离膜222和第二极片沿卷绕方向A卷绕并形成卷绕结构。
需要说明的是，通过上述电极组件22的制造方法制造出的电极组件22的相关结构，可参见上述各实施例提供的电极组件22。
请参照图14，图14为本申请一些实施例提供的电极组件22的制造设备2000的示意性框图，制造设备2000包括提供装置2100和组装装置2200，提供装置2100用于提供负极极片220和正极极片221，组装装置2200用于将负极极片220和正极极片221沿卷绕方向A卷绕并形成卷绕结构。
其中，卷绕结构包括弯折区B，负极极片220和正极极片221均包括位于弯折区B的多个弯折部223。负极极片220中的至少一个弯折部223为第一弯折部224，第一弯折部224外侧的单位面积活性物质容量大于第一弯折部224内侧的单位面积活性物质容量；和/或，正极极片221中的至少一个弯折部223为第二弯折部225，第二弯折部225外侧的单位面积活性物质容量大于第二弯折部225内侧的单位面积活性物质容量。
在一些实施例中，提供装置2100还用于提供将正极极片221和负极极片220隔离的隔离膜222。组装装置2200用于将第一极片、隔离膜222和第二极片沿卷绕方向A卷绕并形成卷绕结构。
通过上述制造设备2000制造出的电极组件22的相关结构，可参见上述各实施例提供的电极组件22。
此外，在本申请实施例还提供一种电极组件22的CB值测试方法，CB值测试步骤如下：
步骤1)：正极单面活性物质层的平均放电容量测试。取上述各实施例的正极极片221，利用冲片模具获得含正极单面活性物质层的小圆片。以金属锂片为对电极，Celgard膜为隔离膜，溶解有LiPF6(1mol/L)的EC+DMC+DEC(体积比为1:1:1的碳酸乙烯酯、碳酸二甲酯、碳酸二乙酯)的溶液为电解液，在氩气保护的手套箱中组装6个相同的CR2430型扣式电池。①电池组装完后静置12h，②在0.1C的充电电流下进行恒流充电，直到电压到达上限截止电压x1V，然后保持电压x1V进行恒压充电，直到电流为50uA，③静置5min，④最后在0.1C的放电电流下进行恒流放电，直到电压到达下限截止电压y1V，⑤静置5min,重复2-5步骤，记录第2次循环的放电容量。6个扣式电池放电容量的平均值即为正极单面活性物质层的平均放电容量。例如，当正极活性材料为磷酸铁锂(LFP)时，上限截止电压x1V＝3.75V，下限截止电压y1V＝2V。当正极活性材料为锂镍钴锰氧化物(NCM)时，上限截止电压x1V＝4.25V，下限截止电压y1V＝2.8V。
步骤2)：负极单面活性物质层的平均充电容量测试。取上述各实施例的负极极片220，利用冲片模具获得与上述步骤1)中正极小圆片面积相同且包含负极单面膜层的小圆片。以金属锂片为对电极，Celgard膜为隔离膜，溶解有LiPF6(1mol/L)的EC+DMC+DEC(体积比为1:1:1的碳酸乙烯酯、碳酸二甲酯、碳酸二乙酯)的溶液为电解液，在氩气保护的手套箱中组装6个CR2430型扣式电池。①电池组装完后静置12h，②在0.05C的放电电流下进行恒流放电，直到电压到达下限截止电压y2mV，③然后再用50uA的放电电流进行恒流放电，直到电压达到下限截止电压y2mV，④静置5min，⑤接着用10uA的放电电流进行恒流放电，直到达到下限截止电压y2mV，⑥静置5分钟，⑦最后在0.1C的充电电流下进行恒流充电，直到最终电压达到上限截至电压x2V，⑧静置5分钟，重复2-8步骤，记录第2次循环的充电容量。6个扣式电池充电容量的平均值即为负极单面膜层的平均充电容量。例如，当负极活性材料为石墨时，上限截止电压x2V＝2V，下限截止电压y2V＝5mV。当负极活性材料为硅时，上限截止电压x2V＝2V，下限截止电压y2V＝5mV。
步骤3)：根据CB值＝上述负极单面活性物质层的平均充电容量(mAh)/上述正极单面活性物质层的平均放电容量(mAh)，计算得出CB值。
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。
以上实施例仅用以说明本申请的技术方案，并不用于限制本申请，对于本领域的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。

Claims (21)

  1. 一种电极组件，包括负极极片和正极极片，所述负极极片和所述正极极片沿卷绕方向卷绕并形成卷绕结构，所述卷绕结构包括弯折区；
    所述负极极片和所述正极极片均包括位于所述弯折区的多个弯折部；
    其中，所述负极极片中的至少一个弯折部为第一弯折部，所述第一弯折部外侧的单位面积活性物质容量大于所述第一弯折部内侧的单位面积活性物质容量；和/或，所述正极极片中的至少一个弯折部为第二弯折部，所述第二弯折部外侧的单位面积活性物质容量大于所述第二弯折部内侧的单位面积活性物质容量。
  2. 根据权利要求1所述的电极组件，其中，所述负极极片中的至少一个弯折部为所述第一弯折部，所述正极极片中的至少一个弯折部为所述第二弯折部，所述第一弯折部的外侧布置有与所述第一弯折部相邻的所述第二弯折部。
  3. 根据权利要求1所述的电极组件，其中，所述负极极片中的至少一个弯折部为所述第一弯折部；
    所述正极极片中与所述第一弯折部相邻的弯折部为第三弯折部；
    所述第三弯折部外侧的单位面积活性物质容量等于所述第三弯折部内侧的单位面积活性物质容量。
  4. 根据权利要求1所述的电极组件，其中，所述正极极片中的至少一个弯折部为所述第二弯折部；
    所述负极极片中与所述第二弯折部相邻的弯折部为第四弯折部；
    所述第四弯折部外侧的单位面积活性物质容量等于所述第四弯折部内侧的单位面积活性物质容量。
  5. 根据权利要求1-3任一项所述的电极组件，其中，所述第一弯折部包括第一集流部、第一活性物质部和第二活性物质部；
    所述第一集流部在其厚度方向上具有相对布置的第一内表面和第一外表面，所述第一活性物质部设于所述第一外表面，所述第二活性物质部设于所述第一内表面。
  6. 根据权利要求5所述的电极组件，其中，所述第二活性物质部的材料与所述第一活性物质部的材料相同；
    所述第一活性物质部的厚度大于所述第二活性物质部的厚度。
  7. 根据权利要求6所述的电极组件，其中，所述第一弯折部还包括第一导电部，所述第一导电部连接于所述第二活性物质部与所述第一内表面之间，所述第一活性物质部的厚度等于或大于所述第二活性物质部与所述第一导电部的总厚度。
  8. 根据权利要求5所述的电极组件，其中，所述第一活性物质部的厚度与所述第二活性物质部的厚度相等；
    所述第一活性物质部中的活性材料的克容量大于所述第二活性物质部中 的活性材料的克容量。
  9. 根据权利要求1、2或4所述的电极组件，其中，所述第二弯折部包括第二集流部、第三活性物质部和第四活性物质部；
    所述第二集流部在其厚度方向上具有相对布置的第二内表面和第二外表面，所述第三活性物质部设于所述第二外表面，所述第四活性物质部设于所述第二内表面。
  10. 根据权利要求9所述的电极组件，其中，所述第四活性物质部的材料与所述第三活性物质部的材料相同；
    所述第三活性物质部的厚度大于所述第四活性物质部的厚度。
  11. 根据权利要求10所述的电极组件，其中，所述第二弯折部还包括第二导电部，所述第二导电部连接于所述第四活性物质部与所述第二内表面之间，所述第三活性物质部的厚度等于或大于所述第四活性物质部与所述第二导电部的总厚度。
  12. 根据权利要求9所述的电极组件，其中，所述第三活性物质部的厚度与所述第四活性物质部的厚度相等；
    所述第三活性物质部中的活性材料的克容量大于所述第四活性物质部中的活性材料的克容量。
  13. 根据权利要求1-12任一项所述的电极组件，其中，所述负极极片包括负极集流体和设置于负极集流体厚度方向上的两侧的负极活性物质层；
    每个负极活性物质层沿所述卷绕方向等厚地分布于所述负极集流体。
  14. 根据权利要求1-13任一项所述的电极组件，其中，所述正极极片包括正极集流体和设置于正极集流体厚度方向上的两侧的正极活性物质层；
    每个正极活性物质层沿所述卷绕方向等厚地分布于所述正极集流体。
  15. 根据权利要求1-14任一项所述电极组件，其中，所述负极极片中的全部弯折部均为所述第一弯折部。
  16. 根据权利要求1-15任一项所述电极组件，其中，所述正极极片中的全部弯折部均为所述第二弯折部。
  17. 一种电池单体，包括外壳和根据权利要求1-16任一项所述的电极组件；
    所述电极组件容纳于所述外壳内。
  18. 一种电池，包括箱体和根据权利要求17所述的电池单体；
    所述电池单体容纳于所述箱体内。
  19. 一种用电设备，包括权利要求18所述的电池。
  20. 一种电极组件的制造方法，包括：
    提供正极极片和负极极片；
    将所述负极极片和所述正极极片沿卷绕方向卷绕并形成卷绕结构；
    其中，所述卷绕结构包括弯折区，所述负极极片和所述正极极片均包括位于所述弯折区的多个弯折部；
    所述负极极片中的至少一个弯折部为第一弯折部，所述第一弯折部外侧 的单位面积活性物质容量大于所述第一弯折部内侧的单位面积活性物质容量；和/或，所述正极极片中的至少一个弯折部为第二弯折部，所述第二弯折部外侧的单位面积活性物质容量大于所述第二弯折部内侧的单位面积活性物质容量。
  21. 一种电极组件的制造设备，包括：
    提供装置，用于提供正极极片和负极极片；以及
    组装装置，用于将所述负极极片和所述正极极片沿卷绕方向卷绕并形成卷绕结构；
    其中，所述卷绕结构包括弯折区，所述负极极片和所述正极极片均包括位于所述弯折区的多个弯折部；
    所述负极极片中的至少一个弯折部为第一弯折部，所述第一弯折部外侧的单位面积活性物质容量大于所述第一弯折部内侧的单位面积活性物质容量；和/或，所述正极极片中的至少一个弯折部为第二弯折部，所述第二弯折部外侧的单位面积活性物质容量大于所述第二弯折部内侧的单位面积活性物质容量。
PCT/CN2021/075357 2021-02-04 2021-02-04 电极组件、电池单体、电池及电极组件的制造设备和方法 WO2022165727A1 (zh)

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